In this study, two kinds of methodology are proposed for incorporating total column zone data from the Total Ozone Mapping Spectrometer (TOMS) into initial conditions of a mesoscale prediction model. The first methodology is based on the strong linear correlation between vertical mean potential vorticity (MPV) and TOMS ozone (O3). The second methodology assimilates the TOMS ozone observations directly by adding the ozone transport equation into the MM5 model and its adjoint. The three... Show moreIn this study, two kinds of methodology are proposed for incorporating total column zone data from the Total Ozone Mapping Spectrometer (TOMS) into initial conditions of a mesoscale prediction model. The first methodology is based on the strong linear correlation between vertical mean potential vorticity (MPV) and TOMS ozone (O3). The second methodology assimilates the TOMS ozone observations directly by adding the ozone transport equation into the MM5 model and its adjoint. The three-dimensional ozone initial condition for the transport equation is estimated from the observed ozone. The proposed first approach of ozone assimilation is applied to two case studies. The first case is the notable Washington D. C. snow storm (to be called DCSTORM) that occurred between 24 - 25 January 2000 along the East Coast of the United States. The second case is an Atlantic Ocean winter storm that was observed between 14-16 February 1997 (to be called AOSTORM). It is found that adjustments in model initial conditions assimilating TOMS ozone-only data are confined to the upper levels and produced almost no impact to the prediction of the storm development. However, when TOMS ozone data are used together with radiosonde observations, a more rapid deepening of the sea level pressure of the simulated storm is observed than with radiosonde-only observations. The predicted motion of the DCSTORM is also altered, with a track closer to the coast. On the contrary, assimilation of only TOMS ozone data produces non-negligible adjustment of wind and temperature fields at all levels in the AOSTORM case. When compared with dropsonde observations, TOMS ozone data improves model forecasts of both temperature and moisture fields. Adjoint sensitivity studies indicate that the significant impact of TOMS ozone on cyclone prediction is expected if large TOMS ozone anomalies appear in a region where model error is grow. Show less

The ability to construct radial wind profiles of tropical cyclones (TC) from limited observations is crucial to the initialization of TC simulations and predictions. A minimum requirement for constructing a reasonable radial wind profile is a high skill in estimating one of the four TC characteristic parameters, namely maximum wind speed (Vmax), radius of maximum wind speed (rmax), 17 ms−1 wind speed (V17), and radius of 17 ms−1 wind (r17) from the other three. In this study, we put froth an... Show moreThe ability to construct radial wind profiles of tropical cyclones (TC) from limited observations is crucial to the initialization of TC simulations and predictions. A minimum requirement for constructing a reasonable radial wind profile is a high skill in estimating one of the four TC characteristic parameters, namely maximum wind speed (Vmax), radius of maximum wind speed (rmax), 17 ms−1 wind speed (V17), and radius of 17 ms−1 wind (r17) from the other three. In this study, we put froth an absolute angular momentum (AAM) based analytical model for inferring the radial profile beyond the rmax from observations of these four parameters. An observed AAM loss L is defined as the ratio of the observed AAM at r17 to that at rmax. We parameterize the observed AAM loss L as an analytical function of these four parameters and environmental factors. The combination of analytical expressions of the AAM loss L and the AAM at r17 and rmax, gives us the analytical model. This observation-physics model allows us to construct radial profiles of TCs under four different configurations from observations of these four parameters. Specifically, we can use Vmax and rmax as inputs for solving (a) the tangential velocity profile of a TC from rmax to r17 or (b) the TC's radius for a given tangential velocity from Vmax to V17. Alternatively, we can use V17 and r17 as inputs for solving (c) the tangential velocity profile of a TC from r17 to rmax or (d) the TC's radius for a given tangential velocity from V17 to Vmax. This enables us to acquire radial wind profiles when one of the four parameters is not available in observations. The degree of consistency of (a) versus (c) and (b) versus (d) is an indicator of the robustness of the model. We evaluate the skill of our model using 4491 records of 197 named TCs derived from the Extended Best Track Dataset for the period of 1998-2016, and find that the mean errors in estimating Vmax, rmax, V17, and r17 are, respectively, 5.95 m/s, 25.37 km, 3.33 m/s, and 57.67 km. The proposed model has several advantages over widely recognized existing TC wind profile models. Most empirical models, for example, are designed to construct radial wind profiles in only one of the four configurations. While other physics-based models have mean errors in Vmax, rmax, and r17 that are larger by several factors. Furthermore, our model can yield physically realistic radial wind profiles and solutions of TC characteristic parameters (meaning that for radial wind profiles, wind velocity decreases monotonically from rmax to r17, and for solutions, Vmax > V17 > 0 and r17 > rmax > 0) for all 4491 TC records, regardless of which of the four configurations is chosen. For more than 10% of the TC records, however, other physics-based models have radial wind profiles that are discrete or increases from the inside to outside, and have solutions that either do not exist or are not physical under certain configurations. Show less

Date Issued

2019

Identifier

2019_Summer_Yan_fsu_0071E_15321

Format

Thesis

Title

The Accuracy of the National Hurricane Center's United States Tropical Cyclone Landfall Forecasts in the Atlantic Basin (2004–2012).

This study examined the position, timing, and intensity of each National Hurricane Center's (NHC) Official Forecasts (OFCL) for Atlantic tropical storms and hurricanes that made landfall in the United States from 2004 to 2012. During that time period, one hundred and fifty tropical cyclones developed in the Atlantic basin. Thirty-two of the cyclones made landfall in the United States as tropical storms or hurricanes. Accurate predictions of the location, timing, and intensity of tropical... Show moreThis study examined the position, timing, and intensity of each National Hurricane Center's (NHC) Official Forecasts (OFCL) for Atlantic tropical storms and hurricanes that made landfall in the United States from 2004 to 2012. During that time period, one hundred and fifty tropical cyclones developed in the Atlantic basin. Thirty-two of the cyclones made landfall in the United States as tropical storms or hurricanes. Accurate predictions of the location, timing, and intensity of tropical cyclone landfalls are important, so that people in a storm's track can prepare adequately for heavy to catastrophic wind, rain, and storm surge. The errors of each of the OFCL for Atlantic tropical storms and hurricanes that made landfall in the United States during 2004–2012 are acquired from the Best Track data set. The ELTOPO1 landmask is used to find the forecasted landfall point using sequential locations from the OFCL offshore and onshore points of each forecast. The great circle distance between the forecasted and actual landfall constitutes the location error. The official landfall time is subtracted from the forecasted landfall time to find the timing error, and the official landfall wind speed is subtracted from the closest to onshore wind speed to find intensity error. There is a trend of decreasing error in location, timing, and intensity forecasting with decreasing lead time. An improvement in tropical cyclone landfall forecasting is found from comparing the 2004–2012 Atlantic landfall forecast errors to those in a study of 1976-2000 forecasts. Show less

ABSTRACT The bias adjustment of visually estimated ship winds in the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) is addressed through the comparison to the QuickSCAT scatterometer equivalent neutral winds. We assume that visually estimated winds and satellite scatterometer winds share similar characteristics, which are a function of stress rather than wind speed, and treat the estimated ship winds as equivalent neutral winds. Under such an assumption, we use statistical... Show moreABSTRACT The bias adjustment of visually estimated ship winds in the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) is addressed through the comparison to the QuickSCAT scatterometer equivalent neutral winds. We assume that visually estimated winds and satellite scatterometer winds share similar characteristics, which are a function of stress rather than wind speed, and treat the estimated ship winds as equivalent neutral winds. Under such an assumption, we use statistical analyses to calculate the bias correction for estimated ship winds. Because observation practices vary by country and data provider, ICOADS identifies datasets by "deck" which is a number that allows for differentiating the source of the records (different deck numbers indicate different data collections provided to ICOADS, each which may contain one or more sources/countries). Three ICOADS decks 792, 926, and 992 contain the vast majority (~90%) of collocated visually estimated ship winds covering the time period November 1999-October 2009. The Root-Mean-Square difference between these visually estimated ship winds and scatterometer winds are 3.0ms-1, 2.8ms-1 and 2.9ms-1 for each major deck respectively. Following the methodology of Freilich (1997) and Freilich and Dunbar (1999), we numerically show that for lower wind speeds (0ms-1-5ms-1 in this case) that the random error in the component of the visually estimated ship winds causes an artificial appearance of an overestimation relative to satellite scatterometer winds. We also extend this statistical artifact test to test higher wind speeds (12ms-1-18ms-1 in this case) through a Monte Carlo approach. An apparent slight drop of the conditional sample means relative to reference line is shown to be a statistical artifact. These artificial biases are properly accounted in this study. A new bias correction, LMS correction, is calculated and also compared to prior corrections such as Lindau (1995). This new bias correction is available for wind speeds ranging from 0ms-1 to 17ms-1, because there are too few spatial and temporal collocated matches at wind speed greater than 17ms-1. We are limited in our ability to perform the adjustments required for intercallibration because when comparing visual winds to scatterometer winds the necessary wind speed observations are rare and small in magnitude. Show less

Date Issued

2016

Identifier

FSU_2016SP_Li_fsu_0071N_13246

Format

Thesis

Title

Aerosol Iron Solubility: Observations from the Atlantic and Pacific Oceans.

Large portions of the world ocean are less productive than they should be based on their nutrient concentrations. Dubbed high-nutrient low-chlorophyll (HNLC) regions, primary productivity in these areas may be limited by any number of factors including high zooplankton grazing rates as well as light and silicon limitation but, in general, iron (Fe) appears to most often be the factor limiting production. With approximately 30% of the world ocean comprised of Fe-limited HNLC waters, it is... Show moreLarge portions of the world ocean are less productive than they should be based on their nutrient concentrations. Dubbed high-nutrient low-chlorophyll (HNLC) regions, primary productivity in these areas may be limited by any number of factors including high zooplankton grazing rates as well as light and silicon limitation but, in general, iron (Fe) appears to most often be the factor limiting production. With approximately 30% of the world ocean comprised of Fe-limited HNLC waters, it is clear that the input of Fe to these waters, and its subsequent bioavailability, has an important role in stimulating primary productivity and lowering pCO2 possibly moderating the rise of atmospheric CO2 concentrations and therefore could influence the planet's climate. The work described in this dissertation represents an effort to characterize the elemental solubility, including Fe, of marine aerosols. The research was conducted on four oceanographic research cruises in the North Atlantic and Pacific Oceans. In total, over 170 aerosol samples were collected in both total and size-fractionated samples. Precipitation events were sampled when possible to characterize the wet deposition of marine aerosols. The data will constrain estimates of aerosol Fe deposition to HNLC regions and improve models of the global carbon cycle. Elemental solubilities were measured using both seawater and ultrapure deionized water leaching methods under trace metal clean conditions. Leaching of the aerosol samples was conducted using a rapid exposure, small volume technique. Ultrapure deionized water leaches were analyzed directly by high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS), a relatively simple analysis technique. Soluble Fe in seawater leaches was analyzed by HR-ICP-MS following column extraction. Additionally, soluble aerosol Fe(II) was measured on four of the cruises. The sampling and analytical methods will be discussed in this dissertation and the results compared with similar studies of aerosol chemistry. The relationship between seawater and deionized water leaching was investigated to evaluate the applicability of the relatively simple ultrapure water technique to prediction of aerosol solubility in seawater. Elemental solubility behavior was analyzed within the context of a host of potential controlling factors including aerosol acidity, source region, and elemental composition among others. The results from these research cruises suggest that aerosol Fe solubility is relatively consistent globally. The solubility of aerosol Fe in deionized water was calculated to be ~12% and ~9% in filtered surface seawater. Aerosol Fe solubility percentage showed no significant correlation with the concentration of acidic aerosol species. The episodic nature of dust events was apparent from the highly variable measured concentrations of aerosol material and no apparent first order relationship existed between the concentration of crustal aerosol species (i.e. Fe) and their respective concentrations in the surface ocean. A robust relationship was found between the concentrations of the ultrapure deionized water and seawater soluble aerosol Fe and a predictive power law equation was derived. Show less

Hosten, Amana, Nicholson, Sharon E., Chagnon, Jeffrey M., Hart, Robert E., Florida State University, College of Arts and Sciences, Department of Earth, Ocean and Atmospheric... Show moreHosten, Amana, Nicholson, Sharon E., Chagnon, Jeffrey M., Hart, Robert E., Florida State University, College of Arts and Sciences, Department of Earth, Ocean and Atmospheric Science Show less

Abstract/Description

The African Easterly Jet (AEJ) is one of the phenomena driving regional as well as global atmospheric circulation. Specifically, within the Sahel region, the AEJ and African Eastern Waves (AEWs) are main features that are linked and associated with the West African Monsoon. Both features determine rainfall and tropical cyclone development in this region. For certain years, the AEJ has a double core structure during the month of August when the jet is the strongest. The goal of this study is... Show moreThe African Easterly Jet (AEJ) is one of the phenomena driving regional as well as global atmospheric circulation. Specifically, within the Sahel region, the AEJ and African Eastern Waves (AEWs) are main features that are linked and associated with the West African Monsoon. Both features determine rainfall and tropical cyclone development in this region. For certain years, the AEJ has a double core structure during the month of August when the jet is the strongest. The goal of this study is to identify distinct cases of the AEJ structure and determine the possible effect on AEW development. For this study, zonal and meridional wind data at 600 hPa was obtained from NCEP reanalysis during the month of August from 1948 to 2016. Maps of zonal wind were made to show the structure of the AEJ. Hovmöller diagrams of the 2.5 to 6-day meridional wind and maps of meridional wind variance were made to show the strength and track of AEWs. Results identified distinct cases where the structure of the AEJ deviated from its long-term mean, including the western (eastern) core being located north relative to the eastern (western) core. The double core cases with the southward eastern core has significantly stronger AEW activity with longer average tracks. However, on inter-annual scales, there is not a strong link between the AEW activity and east Atlantic tropical cyclone activity. The difference between the cases provide valuable insight about the relationship between the AEJ, easterly waves and tropical cyclone formation at the West African coast. Show less

Date Issued

2018

Identifier

2018_Su_Hosten_fsu_0071N_14570

Format

Thesis

Title

African Easterly Waves and Their Relationship to Rainfall on a Daily Timescale.

African Easterly Waves (AEWs) are mesoscale synoptic features that form in West Africa and propagate westward. The relationship of AEWs to rainfall in the region has been examined in previous studies but no scientific consensus has been reached. This relationship, however, has been found to be complex and to involve numerous feedback mechanisms such as the African Easterly Jet (AEJ) fluctuations. Other mechanisms like latent heat release and the temperature gradient at the surface between the... Show moreAfrican Easterly Waves (AEWs) are mesoscale synoptic features that form in West Africa and propagate westward. The relationship of AEWs to rainfall in the region has been examined in previous studies but no scientific consensus has been reached. This relationship, however, has been found to be complex and to involve numerous feedback mechanisms such as the African Easterly Jet (AEJ) fluctuations. Other mechanisms like latent heat release and the temperature gradient at the surface between the dry Sahara Desert and the moist maritime region along the Gulf of Guinea also play a role in the relationship between rainfall and AEWs. This study will investigate the relationship of AEWs to rainfall through objective analysis of the waves and an EOF analysis of daily rainfall over a prescribed region. Two classification schemes along with statistical techniques were used to investigate the spatiotemporal variability of the relationship between African Easterly Waves (AEWs) and the rainfall over West Africa. Two varying methods were used because of the highly subjective manner of tracking AEWs. This study was limited to four wet years (1958 â1961) and four dry years (1982-1985) during the summer months of June, July, August and September. The first technique was a new three-step method designed by Dr. A. Fink that makes use of 700mb and 850mb streamline plots and band-pass filtered meridional wind data. The second method uses the vertical structure of the band-pass filtered meridional wind to identify wave passage. The methods were compared and contrasted with one another, and both were shown to be adequate for tracking AEWs. However, for examining the relationship of rainfall with AEWs the second method appropriately named the Vertical Profile Method (VPM) was found to be preferable. Using the VPM the difference between wave characteristics and rainfall variability were examined on a daily timescale. This involved creating daily rainfall datasets for four different quadrants over the Sahel and relating any changes in rainfall activity to the AEWs as they both propagated across the quadrants. The differences in AEW and rainfall characteristics were examined by making comparisons within two distinct time-frame perspectives. The first perspective examined differences between wet and dry years and the second perspective examined differences between the 1st two months (June-July) and the last two months (August-September). For each category the strength of the waves, number of waves, location of the north and south regime, rainfall distribution and rainfall amounts were compared. During the wet years (1958 -1961) the number of waves that propagated across West Africa averaged 59 waves per year using the Vertical Profile Method (VPM) and 49 using the Andreas Fink Method (AFM). The number of AEWs tracked during the dry years (1982-1985) averaged about 63 with the VPM and 54 with the AFM. The difference in the average number of AEWs between the methods was probably a result of the limitations of each method. More waves in the dry years supports previous conclusions that stronger but less frequent AEWs occur in wet years and weaker but more frequent AEWs occur in the dry years. Tracking of the AEWs also allowed for the separation of the AEWs into two distinct wave regimes north and south of the African Easterly Jet (AEJ). Throughout all eight years the separation became apparent as the summer progressed with the separation reaching a maximum. This coincides with the fluctuations in AEJ intensity, which also has a maximum in the month of August. Rainfall within the tracked AEWs was found to be bimodal with the region of maximum northerly flow containing the most rainfall. This region is ahead of the trough and is typically associated with squall line convective activity. The maximum region was the same for both wet and dry years and also for the two month season comparison. An EOF analysis of daily rainfall was completed for 1958 (wet year) and 1983 (dry year) to determine if any relationship to AEWs could be identified in the rainfall time series. The resulting eigenvalues show the influence of topography along the Guinea coast with positive values: however, no discernable link to AEWs was present. The power spectrum of the first two principle components did identify a significant peak at the same period associated with AEWs. This power spectrum analysis demonstrated that rainfall is linked to AEWs, but a more detailed dynamical investigation is needed. Show less

With the events of recent years - especially in the Atlantic tropical basin, the need for additional forecast tools to aid in tropical cyclone (TC) prediction and understanding is apparent. A suite of algorithms to be used for 3-D TC visualization are presented. Utilizing the assets of the Amira visualization software, we present methods which constitute a real-time visualization routine of TC genesis, mesoscale, and TC centered features derived from the The Florida State University (FSU)... Show moreWith the events of recent years - especially in the Atlantic tropical basin, the need for additional forecast tools to aid in tropical cyclone (TC) prediction and understanding is apparent. A suite of algorithms to be used for 3-D TC visualization are presented. Utilizing the assets of the Amira visualization software, we present methods which constitute a real-time visualization routine of TC genesis, mesoscale, and TC centered features derived from the The Florida State University (FSU) adaptation of the Pennsylvania State University (PSU) and National Center for Atmospheric Research (NCAR) Fifth Generation Mesoscale Model (MM5). However, the algorithms we develop are generic in that they can be applied to any gridded output from a forecast model. A method for the removal TC vorticity fields allowing an approximation of the environmental steering levels is also developed. The development and use of an adaptive wavenumber refinement filter (AWRF) has proven to outperform various alternative methods for TC vortex removal and thus the preservation of the environmental flow. Case study inter-comparisons are performed and illustrate that the AWRF provides the smallest mean track errors in future forecast position compared to those determined by the model's use of minimum sea level pressure (SLP) and vorticity maxima algorithm for TC center location. Discussions are also provided suggesting areas of needed improvement within the algorithm as illustrated by the case studies presented. Show less

The nature of balance in the atmosphere is of central importance to the dynamics of both the troposphere and the stratosphere, and unbalanced motions such as inertia-gravity waves play a significant role in many aspects of atmospheric behavior. In light of the importance of upper-tropospheric jets for the generation of inertia-gravity waves in the atmosphere, this study examines the evolution of unstable barotropic jets to assess the nature and evolution of balance in these features. This... Show moreThe nature of balance in the atmosphere is of central importance to the dynamics of both the troposphere and the stratosphere, and unbalanced motions such as inertia-gravity waves play a significant role in many aspects of atmospheric behavior. In light of the importance of upper-tropospheric jets for the generation of inertia-gravity waves in the atmosphere, this study examines the evolution of unstable barotropic jets to assess the nature and evolution of balance in these features. This issue is explored using the simplest non-trivial dynamical framework in which balanced and unbalanced flows can coexist, namely the one-layer shallow water equations. In this study, numerical simulations of initially balanced zonal barotropic jets on an f plane are investigated for evidence of the breakdown of balance and the generation of inertia-gravity waves during the life cycles of the instabilities to these jets. In these simulations, the parameters of the basic-state jet (i.e., jet width and speed) are varied systematically in an attempt to elucidate the dependence of balance on the structure and dynamical evolution of the instability. The presence of unbalanced flow, either in numerical simulations or in atmospheric data, is typically inferred via various quantities that provide indirect measures of imbalance, such as the existence of strong ageostrophy, large Rossby and/or Lagrangian Rossby numbers, and large values of horizontal divergence and its material derivative. Along with evaluating these parameters in each simulation, a potential vorticity inversion method is employed to obtain the structure of balanced and unbalanced fields within each simulation. The diagnostic calculations are then compared to the potential vorticity inversion results. Contrasts and comparisons are presented for each of the simulations shown in this study. The simulations consist of an unstable barotropic wave ranging from small (i.e., O(10-1)) Rossby and Froude number to large (i.e., O(1)) Rossby and Froude number. For strong jets, neither the Rossby number nor the Froude number is small compared to unity therefore the applicability of traditional scale analysis is unclear (e.g. Haltiner and Williams, 1980) (i.e., the balance condition is no longer valid and a breakdown of balance should occur). In contrast, the results of the diagnostic calculations and potential vorticity inversions reveal that nonlinear balance is essentially valid for this particular jet profile, even though the Rossby and Froude numbers are O(1) for the strong barotropic jet. Significant inertia-gravity wave structures were not found in any of the cases shown here, which is consistent with the results obtained by several other investigators in their integrations of the shallow-water equations. Show less

Integrated kinetic energy (IKE) is a recently developed metric that approximates the destructive potential of a tropical cyclone by assessing the size and strength of its wind field. Despite the potential usefulness of the IKE metric, there are few, if any, operational tools that are specifically designed to forecast IKE in real-time. Therefore, IKE and tropical cyclone structure are analyzed within historical Atlantic tropical cyclones from the past two decades in order to develop an... Show moreIntegrated kinetic energy (IKE) is a recently developed metric that approximates the destructive potential of a tropical cyclone by assessing the size and strength of its wind field. Despite the potential usefulness of the IKE metric, there are few, if any, operational tools that are specifically designed to forecast IKE in real-time. Therefore, IKE and tropical cyclone structure are analyzed within historical Atlantic tropical cyclones from the past two decades in order to develop an understanding of the environmental and internal storm-driven processes that govern IKE variability. This analysis concurs with past research that IKE growth and decay is influenced by both traditional tropical cyclone development mechanisms and by other features such as extratropical transition and trough interactions. Using this framework, a series of statistical prediction tools are created in an effort to project IKE in Atlantic tropical cyclones from a series of relevant normalized input parameters. The resulting IKE prediction schemes are titled the "Statistical Prediction of Integrated Kinetic Energy (SPIKE)". The first version of SPIKE utilizes simple linear regression to project historical IKE quantities in a perfect prognostic mode for all storms between 1990 and 2011. This primitive model acts as a proof of concept, revealing that IKE can be skillfully forecasted relative to persistence out to 72 hours by even the simplest of statistical models if given accurate estimates of various metrics measured throughout the storm and its environment. The proof-of-concept version of SPIKE is improved upon in its second version, SPIKE2, by incorporating a more sophisticated system of adaptive statistical models. A system of artificial neural networks replaces the linear regression model to better capture the nonlinear relationships in the TC-environment system. In a perfect prognostic approach with analyzed input parameters, the neural networks outperform the linear models in nearly every measurable way. The system of neural networks is also more versatile, as it is capable of producing both deterministic and probabilistic tools. Overall, the results from these perfect prognostic exercises suggest that SPIKE2 has a high potential skill level relative to persistence and several other benchmarks. Finally, in an effort to assess its real-time performance, the SPIKE2 forecasting system is run in a mock-operational hindcast mode for the 1990 to 2011 North Atlantic hurricane seasons. Hindcasts of IKE are produced in this manner by running the neural networks with hindcasted input parameters from NOAA's second generation Global Ensemble Forecast System reforecast dataset. Ultimately, the results of the hindcast exercises indicate that the neural network system is capable of skillfully forecasting IKE in an operational setting at a level significantly higher than climatology and persistence. Ultimately, forecasts of IKE from these neural networks could potentially be an asset for operational meteorologists that would complement existing forecast tools in an effort to better assess the damage potential of landfalling tropical cyclones, particularly with regards to storm surge damage. Show less

Date Issued

2015

Identifier

FSU_migr_etd-9376

Format

Thesis

Title

Analysis methods for characterizing salinity variability from multivariate time series applied to the Apalachicola Bay estuary.

Creator

Morey, Steven, Dukhovskoy, Dmitry

Abstract/Description

Statistical analysis methods are developed to quantify the impacts of multiple forcing variables on the hydrographic variability within an estuary instrumented with an enduring observational system. The methods are applied to characterize the salinity variability within Apalachicola Bay, a shallow multiple-inlet estuary along the northeastern Gulf of Mexico coast. Thirteen-year multivariate time series collected by the National Estuary Research Reserve at three locations within the bay are... Show moreStatistical analysis methods are developed to quantify the impacts of multiple forcing variables on the hydrographic variability within an estuary instrumented with an enduring observational system. The methods are applied to characterize the salinity variability within Apalachicola Bay, a shallow multiple-inlet estuary along the northeastern Gulf of Mexico coast. Thirteen-year multivariate time series collected by the National Estuary Research Reserve at three locations within the bay are analyzed to determine how the estuary responds to variations in external forcing mechanisms, such as freshwater discharge, precipitation, tides and local winds, at multiple time scales. The analysis methods are used to characterize the estuarine variability under differing flow regimes of the Apalachicola River, a managed waterway, with particular focus on extreme events and scales of variability that are critical to local ecosystems. Multivariate statistical models are applied that describe the salinity response to winds from multiple directions, river flow, and precipitation at daily, weekly, and monthly time scales to understand the response of the estuary under different climate regimes. Results show that the salinity is particularly sensitive to river discharge and wind magnitude and direction, with local precipitation being largely unimportant. Applying statistical analyses with conditional sampling quantifies how the likelihoods of high salinity and long duration high salinity events, conditions of critical importance to estuarine organisms, change given the state of the river flow. Intraday salinity range is shown to be negatively correlated with the salinity, and correlated with river discharge rate. Show less

Biomass burning and anthropogenic emissions affect the composition of the atmosphere, thereby impacting global climate and health. Deep convective processes can loft emissions from the boundary layer into the upper troposphere or lower stratosphere (UTLS). Strong upper-level winds can potentially transport the emissions over long distances. This study focused on the deep convective transport of biomass burning emissions near the Strait of Malacca during summer. The Weather Research and... Show moreBiomass burning and anthropogenic emissions affect the composition of the atmosphere, thereby impacting global climate and health. Deep convective processes can loft emissions from the boundary layer into the upper troposphere or lower stratosphere (UTLS). Strong upper-level winds can potentially transport the emissions over long distances. This study focused on the deep convective transport of biomass burning emissions near the Strait of Malacca during summer. The Weather Research and Forecasting (WRF) and Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT_4) models were used to investigate deep convection and the transport of emissions from fires in the region. Fire data from the Moderate-resolution Imaging Spectroradiometer (MODIS) sensors onboard the Aqua and Terra satellites provided locations of fire emissions. These fire datasets were obtained from the University of Maryland's Fire Information for Resource Management System (FIRMS). To investigate the deep convective processes thoroughly, this study used high resolution modeling (4 km grid spacing) to resolve the convection explicitly. Explicit resolution allows the thunderstorms to be simulated more realistically than would parameterization, thus making it ideal for this research. Results showed that deep convection occurring in the Strait of Malacca is driven primarily by diurnal heating patterns and the region's topography. Convection in the region is frequent and scattered, but follows a cyclic diurnal pattern: convection over land during daytime and over the Strait during nighttime. When emissions from fires encounter areas of deep convection, they are quickly lofted to the UTLS where winds then transport them elsewhere. Show less

Date Issued

2013

Identifier

FSU_migr_uhm-0216

Format

Thesis

Title

An Analysis of Cyclogenesis for Mid-Latitude and Tropical Storms Using the Petterssen-Sutcliffe Development Equation.

In this study, the Petterssen-Sutcliffe development equation is used to examine cyclogenesis. In the past, several other methods have been used to study cyclogenesis and calculate vertical motion, such as the kinematic and adiabatic methods, quasi-geostrophic theory as well as the approaches derived from them. However, there is little documentation on the application of the historical Petterssen-Sutcliffe method, and hence the motivation for this study. The forcing terms of the Petterssen... Show moreIn this study, the Petterssen-Sutcliffe development equation is used to examine cyclogenesis. In the past, several other methods have been used to study cyclogenesis and calculate vertical motion, such as the kinematic and adiabatic methods, quasi-geostrophic theory as well as the approaches derived from them. However, there is little documentation on the application of the historical Petterssen-Sutcliffe method, and hence the motivation for this study. The forcing terms of the Petterssen-Sutcliffe development equation are calculated using GEMPAK software. These forcing terms include vorticity advection, temperature advection, stability, and diabatic heating. Two mid-latitude storms and two tropical systems were analyzed to see if this method could recognize cyclogenesis in both baroclinic and barotropic environments. The first mid-latitude storm occurred in late January 2000. It formed off the coast of the Carolinas and traveled up the East Coast over the Atlantic Ocean. The second storm spent its life cycle over land in the Mid-Atlantic and New England regions during March 1999. Both tropical systems originated in the Gulf of Mexico: Hurricane Earl (1998) and Hurricane Gordon (2000). This method of analysis was shown to have general success in identifying cyclogenesis of mid-latitude cyclones and somewhat limited success with tropical storms. It is hoped that this method will benefit both educational and operational environments where students and forecasters can use this additional analysis to supplement their understanding of the atmosphere. Show less

Date Issued

2004

Identifier

FSU_migr_etd-4069

Format

Thesis

Title

Analysis of GFDL Intensity Forecasting Performance for Gulf/Caribbean Major Hurricanes from 1998-2008.

Creator

Hazelton, Andrew, Earth, Ocean & Atmospheric Science

Abstract/Description

While both computer model and official track forecasts of Atlantic Basin hurricanes have improved significantly over the past several decades, forecasts of intensity continue to prove difficult. Even specialized hurricane models struggle with predicting intensity. This study analyzes the intensity errors of the Geophysical Fluid Dynamics Laboratory (GFDL) Hurricane Model for 19 major hurricanes over the Gulf of Mexico and Caribbean Sea from 1998 to 2008. Using the measure of skill relative to... Show moreWhile both computer model and official track forecasts of Atlantic Basin hurricanes have improved significantly over the past several decades, forecasts of intensity continue to prove difficult. Even specialized hurricane models struggle with predicting intensity. This study analyzes the intensity errors of the Geophysical Fluid Dynamics Laboratory (GFDL) Hurricane Model for 19 major hurricanes over the Gulf of Mexico and Caribbean Sea from 1998 to 2008. Using the measure of skill relative to the Statistical Hurricane Intensity Forecast (SHIFOR), the GFDL forecasts generally improved throughout most of the 11-year period, although there were some exceptions to this increase in skill. Comparing the GFDL to the Statistical Hurricane Intensity Prediction Scheme (SHIPS), it is found that the GFDL was slightly outperformed by SHIPS on most of the forecast categories and times. It seems that there is a correlation between higher intensity storms and higher errors (R = 0.53), and there is also a clear relationship between large negative errors and rapid intensification (R = 0.62). This relationship is explored for some of the ―higher-error‖ cases by comparing the GFDL forecast intensity progression with the actual intensity change. Hurricanes Dean (2007) and Felix (2007) are also analyzed in more detail, since both of these storms were exceptions to the general trend in increased skill from 2000-2008. It is hoped that this and further analysis will illuminate reasons for the model's difficulty with the intensity forecasts, and provide a basis for improving model forecasts and official forecasts of tropical cyclone intensity. Show less

Statistics of extreme events in weather and climate (e.g. rare floods or strong wind storms) are commonly based on the assumption of Gaussian statistics. Sixty-two years of National Centers for Environmental Prediction / National Center for Atmospheric Research (NCEP / NCAR) Reanalysis I data and thirty-one years of National Centers for Environmental Prediction / Department of Energy (NCEP / DOE) Reanalysis II data are analyzed to determine if this assumption is true. The mean and variance of... Show moreStatistics of extreme events in weather and climate (e.g. rare floods or strong wind storms) are commonly based on the assumption of Gaussian statistics. Sixty-two years of National Centers for Environmental Prediction / National Center for Atmospheric Research (NCEP / NCAR) Reanalysis I data and thirty-one years of National Centers for Environmental Prediction / Department of Energy (NCEP / DOE) Reanalysis II data are analyzed to determine if this assumption is true. The mean and variance of several atmospheric variables are calculated. Furthermore, the higher statistical moments — skewness and kurtosis — are calculated for geopotential height, relative vorticity, and the meridional and zonal wind components. Zonal averages of these higher statistical moments are also analyzed. It is found that statistically significant deviations from Gaussianity are found for every variable in the atmosphere on the synoptic to global scales. This empirical analysis is linked to particular atmospheric phenomena such as tropical cyclones, sudden stratospheric warming events, and the concept of rectifica- tion. In essence, there are fundamental forcing asymmetries in the atmospheric equa- tions of motion that lead to the existence of non-Gaussian distributions. Additionally, the relationship between skewness and kurtosis and the existence of power-law tails in non-Gaussian systems is examined. Show less

At the polar latitudes, maritime mesocyclones form throughout the year, often near or embedded within cloud streets associated with massive cold air outbreaks. Such storms appear on the 100–1000 km horizontal scale. However, polar mesocyclones tend to exist on the lesser end of the horizontal scale. As a storm's size decreases, the likelihood that they will be well-represented in data also decreases. Underrepresentation of polar mesocyclones in reanalyses will affect climatological forecasts... Show moreAt the polar latitudes, maritime mesocyclones form throughout the year, often near or embedded within cloud streets associated with massive cold air outbreaks. Such storms appear on the 100–1000 km horizontal scale. However, polar mesocyclones tend to exist on the lesser end of the horizontal scale. As a storm's size decreases, the likelihood that they will be well-represented in data also decreases. Underrepresentation of polar mesocyclones in reanalyses will affect climatological forecasts and research that utilize such data. Namely, the air-sea interactions associated with polar mesocyclones will be undercut, thereby impacting estimates of ocean circulation. Additionally, many reanalyses underestimate near-surface wind speeds, which is linked to but not exclusively dependent upon the problems associated with data resolution. Harsh polar conditions make regions of scientific interest unfavorable for in situ data collection, which compounds the aforementioned issues. This research examines the relatively new Arctic System Reanalysis (ASRv1) and its ability to represent three polar mesocyclonic systems of differing size. Should ASRv1 represent polar mesocyclones effectively, it could be a prime candidate in establishing an arctic atmospheric state for air-sea modeling. The product is compared to high-resolution Weather Research and Forecasting (WRF) model simulations, with ERA-Interim information providing the initial and boundary conditions. Simulation results are checked against available 10m equivalent neutral wind data from QuikSCAT to ensure that the model is producing reasonable atmospheric conditions. Comparisons are drawn for near-surface wind fields and surface turbulent fluxes to focus on ASRv1's depictions of air-sea interactions for polar mesocyclones. Differences betwixt ASRv1 and the WRF simulations are given with the likely explanations—physical, dynamical, and data-based (e.g., resolution, model options)—behind such differences. Show less

Date Issued

2015

Identifier

FSU_migr_etd-9536

Format

Thesis

Title

Analysis of Prospective Fog Warning Systems Using AWOS/ASOS Station Data Throughout the State of Florida.

Fog and smoke can combine to form dangerous zero visibility conditions along roadways throughout the state of Florida. The ability to forecast when and where fog will occur is problematic. Fog can occur over large and small scales, and is dependent on many meteorological and geographic variables. This study used Automated Weather Observation Stations (AWOS) and Automated Surface Observing Systems (ASOS) throughout the state of Florida to develop a climatology to ascertain what conditions are... Show moreFog and smoke can combine to form dangerous zero visibility conditions along roadways throughout the state of Florida. The ability to forecast when and where fog will occur is problematic. Fog can occur over large and small scales, and is dependent on many meteorological and geographic variables. This study used Automated Weather Observation Stations (AWOS) and Automated Surface Observing Systems (ASOS) throughout the state of Florida to develop a climatology to ascertain what conditions are necessary for radiation fog development. Forecasted dewpoint depression, wind speed, cooling rates, the derived vertical hydrolapse, and other variables were shown to all affect fog formation. Using this information, a fog forecasting model was developed. The model was used to determine a three-hour binary forecast for the early morning hours, every day, at the location of the mesonet stations used. The model would predict fog if meteorological conditions preceding the forecasting time met a series of threshold levels. The goal was to make the model easy to deploy so that law enforcement can make a fast decision of whether to warn the public about potentially dangerous road conditions. The model was compared to other forecasting techniques such as the Model Output Statistics (MOS) fog product and climatology. After comparing the model to reference forecasts, it was found that the model outperformed climatology by a significant margin and was able to detect more fog events than MOS. However, the model had a higher false alarm rate and lower percent forecasts correct compared to MOS . Show less

Date Issued

2014

Identifier

FSU_migr_etd-9236

Format

Thesis

Title

An Analysis of Temporal and Spatial Variations of Surface Albedo over Africa.

Surface albedo is defined as the ratio of the reflected to the incident solar radiation on the earth's surface. Some general circulation model simulations indicate that an increase in albedo due to desertification and deforestation may lead to reduction in precipitation and evapotranspiration. The monthly mean of an earlier surface albedo dataset and MODIS are used to examine the surface albedo spatial and temporal variations of Africa. In order to study surface albedo temporal variations the... Show moreSurface albedo is defined as the ratio of the reflected to the incident solar radiation on the earth's surface. Some general circulation model simulations indicate that an increase in albedo due to desertification and deforestation may lead to reduction in precipitation and evapotranspiration. The monthly mean of an earlier surface albedo dataset and MODIS are used to examine the surface albedo spatial and temporal variations of Africa. In order to study surface albedo temporal variations the African continent is divided into three regions: northern, equatorial and southern. Even though every month is analyzed, only the four months of February, April, July and November are discussed. In the northern region both the earlier dataset and MODIS the surface albedo showed the largest annual range in surface albedo in the semi-arid and arid areas. It is in these areas where the Meteosat surface albedo values were highest. While MODIS also showed a similar annual range in these areas, however this range was over a much smaller area. The spatial variations in surface albedo in the northern region depict the geographical features of the region. Also in the semi-arid and arid areas of the northern region is where the two datasets most differed. The largest differences between the datasets occur in February, which is during the dry season. It is in these areas where the largest surface albedo values were found and these areas are near or are west of major dust sources. In the southern region as was the case in the northern region the semi-arid and arid areas had the largest annual ranges. In the southern region the actual surface albedo for the semi-arid and arid region are lower than the surface albedo in the northern region for the same areas. The two datasets differ the most in the semi-arid and arid areas. To further understand the temporal and spatial variations of surface albedo, two land cover classification schemes were examined. MODIS uses the International Geosphere-Biosphere Programme 17-land cover scheme. A second land cover dataset was created from White/UNESCO vegetation map to be used with the earlier surface albedo dataset. In some areas the maximum albedo occur in the wet season while in other areas maximum albedo occur in the dry season. In the areas where maximum albedo occurs in the wet season, vegetation tended to be the major factor in determining surface albedo. In Charney's classic 1975 paper he theorized that a reduction in vegetation would lead to an increase in surface albedo, which in turn would lead to a reduction in precipitation. In this for a majority of the vegetation groups minima in surface albedo and NDVI occur at the same time of year. These findings do not support Charney's theory that a reduction in vegetation will lead to an increase in surface albedo. Surface albedo may be influenced by an increase in reflective surfaces. One of the objectives of understanding the spatial and temporal variations in surface albedo is to compare model calculated surface albedo to satellite derived surface albedo. A Comparison of Biosphere-Atmosphere Transfer Scheme, Land Surface Model to Advanced Very High Resolution Radiometer lead to the parameterized albedo in the Community Land Model version 2 to be adjusted. As satellite instrumentation improves so must the land surface process of general circulation models. This study shows that the parameterized surface albedo in Community Land Model version 2 still may not correctly represent the semi-arid and arid regions of Africa. The parameterized vegetation and soil albedo values are still too low. Show less

Date Issued

2005

Identifier

FSU_migr_etd-1574

Format

Thesis

Title

Analysis of the 10–20-Day Intraseasonal Oscillation in the Indian Ocean Using Surface Winds from Composite Satellite Data.

The 10–20-day mode of surface winds is examined in the Indian Ocean, with special reference to the Arabian Sea, the Bay of Bengal, and the equatorial Indian Ocean during a strong (1994), weak (2002), and normal (1995) Indian summer monsoon. The winds are from the Cross Calibrated Multi-Platform (CCMP) gridded wind product version 2.0. Results indicate the 10–20-day mode of latitudinally averaged surface winds have zonal propagation in the western Indian Ocean (west of 75°E) and the signal... Show moreThe 10–20-day mode of surface winds is examined in the Indian Ocean, with special reference to the Arabian Sea, the Bay of Bengal, and the equatorial Indian Ocean during a strong (1994), weak (2002), and normal (1995) Indian summer monsoon. The winds are from the Cross Calibrated Multi-Platform (CCMP) gridded wind product version 2.0. Results indicate the 10–20-day mode of latitudinally averaged surface winds have zonal propagation in the western Indian Ocean (west of 75°E) and the signal appears stationary in the eastern Indian Ocean (east of 75°E) during May through September. The meridional propagation of the 10–20-day mode of longitudinally averaged surface winds appears weak during summer monsoon periods. The 10–20-day mode of surface winds in the Arabian Sea and the Bay of Bengal is more energetic than in the equatorial Indian Ocean. The signal of the 10–20-day mode appears more robust during a strong monsoon than during a weak monsoon in the Arabian Sea; however, no significant difference is found in the Bay of Bengal and equatorial Indian Ocean between strong and weak monsoons. Ensemble empirical mode decomposition (EEMD) analysis is used on a time series from the Arabian Sea to create an index for the 10–20-day mode in surface winds. Using this index, 75 cases of 15-phase 10–20-day events are identified and used to create composites of surface winds. Through these composites, a positive surface wind anomaly is found to appear at 60°E, centered on 15°S, and propagate zonally eastward to 90°E before reflecting back to propagate westward and then disperse off the coast of Madagascar. It is proposed that this oscillating positive wind anomaly is a feature of the southernmost cell of the 10–20-day convective double-cell structure that has extended farther south into the southern Indian Ocean and that this mode connects the Arabian Sea and southern Indian Ocean through the Somali Jet and surface winds. Show less

Date Issued

2018

Identifier

2018_Su_RomanStork_fsu_0071N_14803

Format

Thesis

Title

An Analysis of the Extratropical Flow Response to Recurving Atlantic Tropical Cyclones.

Creator

Brannan, Allison, Department of Earth, Ocean and Atmospheric Sciences

Abstract/Description

There is a significant frequency of Atlantic tropical cyclones that complete extratropical transition and recurve in the mid-latitudes. Using a climatological approach, this study will analyze the extratropical flow response to recurving Atlantic tropical cyclones and compare the results to those from the Western North Pacific, as examined by Archambault et al. (2013). This investigation includes 54 recurving Atlantic tropical cyclones occurring between 2007 and 2013. The extratropical flow... Show moreThere is a significant frequency of Atlantic tropical cyclones that complete extratropical transition and recurve in the mid-latitudes. Using a climatological approach, this study will analyze the extratropical flow response to recurving Atlantic tropical cyclones and compare the results to those from the Western North Pacific, as examined by Archambault et al. (2013). This investigation includes 54 recurving Atlantic tropical cyclones occurring between 2007 and 2013. The extratropical flow response will be quantified using potential vorticity. Characteristics of tropical cyclones, the extratropical jet stream, and the dynamical "phasing" of their interaction will be examined to determine the features that lead to significantly amplified extratropical flow. Results show the extratropical flow to be insensitive to the wind speed, latitude, and month of recurvature. However, there is an association between low mean sea level pressure and a larger amplification of flow. Finally, tropical cyclones recurving on the east side of the nearest trough are shown to have "favorable phasing," which yields amplification of the extratropical flow. Show less

Date Issued

2015

Identifier

FSU_migr_uhm-0538

Format

Thesis

Title

Analyzing the Evolution of Tornadic Environments in Landfalling Tropical Cyclones.

Creator

Speransky, Stanislav, Ray, Peter S., Hart, Robert Edward, Bourassa, Mark A., Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric... Show moreSperansky, Stanislav, Ray, Peter S., Hart, Robert Edward, Bourassa, Mark A., Florida State University, College of Arts and Sciences, Department of Earth, Ocean, and Atmospheric Science Show less

Abstract/Description

Previous studies have analyzed various atmospheric tornado parameters in a Tropical Cyclone (TC) environment. This study focuses on the evolution of these parameters through a TC landfall. The TCTOR dataset, which assigns all TC tornadoes to their respective TC, is used to group qualifying events from a pool of 1201 tornadoes during the period of 1995-2010 into eight time intervals relative to TC landfall. The environment is then analyzed using seven operationally used tornado parameters. A... Show morePrevious studies have analyzed various atmospheric tornado parameters in a Tropical Cyclone (TC) environment. This study focuses on the evolution of these parameters through a TC landfall. The TCTOR dataset, which assigns all TC tornadoes to their respective TC, is used to group qualifying events from a pool of 1201 tornadoes during the period of 1995-2010 into eight time intervals relative to TC landfall. The environment is then analyzed using seven operationally used tornado parameters. A statistical, spatial, and sounding analysis is performed to determine how the tornadic environment evolves over time after landfall. Analysis shows that statistically significant differences in the mean value of each parameter are found between pre-landfall, post-landfall, and various time interval comparisons. Composite field charts and case studies show that the wind shear parameters at different vertical layers help explain tornado concentrations in space at different time intervals. In addition, a comparison of composite field charts is made between the larger pool of 32 TCs in the ALL composite and the 10 TCs representing the lowest tercile, with respect to the total number of tornadoes produced. This comparison shows higher magnitudes of shear parameters in the ALL composite. Combined with model derived soundings of three prolific tornado producing TCs, this study shows that the increase in shear in the lowest layer (0-1 km) is the best diagnostic tool to explain the increase in tornado occurrences at TC landfall. This finding supports prior research, which showed that low level shear maxima coincided with tornado locations. The increase in shear in the 0-3 km and 0-6 km layers at later time intervals is found to be the best diagnostic tool to explain the secondary increase in tornado occurrences after 24 hours past TC landfall. Additionally, 24 hours after TC landfall appears to be the critical time that separates weaker TC tornadoes at prior time intervals from stronger ones that resemble mid-latitude cyclone tornadoes that occur after, based on parameter values, hodograph analysis, and conceptual models. Lastly, the Significant Tornado Parameter (STP), used with discretion, is shown to work well in diagnosing tornado occurrence in some time intervals but proves to be a poor tool in others. Show less

Date Issued

2014

Identifier

FSU_migr_etd-9250

Format

Thesis

Title

Annual to Interannual Barotropic Variability in the Atlantic Western Boundary.

A method for estimating deep, depth independent current variability is described. The procedure uses XBT derived dynamic heights to remove the near surface signal from altimetric sea surface height (SSH). The difference between SSH and dynamic height is operationally defined as barotropic height (BRT). Currents are obtained from BRT slopes using the geostrophic balance. The method requires the variability below the deepest XBT measurement to be small. Results are restricted to temporal... Show moreA method for estimating deep, depth independent current variability is described. The procedure uses XBT derived dynamic heights to remove the near surface signal from altimetric sea surface height (SSH). The difference between SSH and dynamic height is operationally defined as barotropic height (BRT). Currents are obtained from BRT slopes using the geostrophic balance. The method requires the variability below the deepest XBT measurement to be small. Results are restricted to temporal variability, as geoid uncertainties in the SSH data render absolute current estimations impossible. The technique is originally developed for use in the Atlantic Western Boundary Current (WBC). Comprehensive verification of the methodology requires simultaneous SSH, XBT and current meter measurements. There are no available Atlantic data sets that meet these requisites. The alternative is to use synthetic data from the CLIPPER Atlantic model (1=6o resolution). Correlation (r) between estimated and modelled near bottom velocities in WBC areas of interest vary from 0.7 to 0.8. Further tests are conducted with observed data from the Shikoku Basin boundary current in southern Japan, where the method is capable of reproducing the directly measured near bottom current variability (r = 0:6). The procedure is also tested using north Pacific (5o ¡ 55oN) data from the OCCAM model. Correlations between model derived and BRT estimated velocities are around r = 0:7 for the Shikoku Basin northern boundary and for the Pacific WBC. Values reach r = 0:9 in large areas of the basin's interior, specially over smooth topography. The above method is used to generate time series of the barotropic variability in two areas of the Atlantic Western Boundary. One site is located at 38oN, inshore of the Gulf Stream. The other is at 8oS, off the Brazilian coast. Both series are a approximately 6 years long. Empirical Orthogonal Function analysis results conducted on SSH and sea surface temperature data are used to confirm the feasibility of applying the method in the chosen South Atlantic area. Currents are compared to scatterometer derived local along-shore wind stress and basin wide wind stress curl. In both areas, current variability is significantly correlated to basin averaged wind stress curl and and also to local along-shore wind stress. The relationship between currents and wind curl is coherent with the WBC response to interior Sverdrup flow. We propose that local wind stress exerts control over the flow by divergence of the Ekman flow at the coast. In the north, the variability is dominated by interannual oscillations of the wind curl. The effects of the local stress are secondary and have annual frequency. Both wind stress curl and along-shore wind are significantly correlated to the currents on the southern site, but the local effect appears to be the dominant forcing. The main observed results are confirmed by data from a numerical model with 1=6o horizontal resolution. Show less

Date Issued

2004

Identifier

FSU_migr_etd-2333

Format

Thesis

Title

Applications of Calcareous Nannofossils and Stable Isotopes to Cenozoic Paleoceanography: Examples from the Eastern Equatorial Pacific, Western Equatorial Atlantic and Southern Indian Oceans.

This dissertation is a collection of five calcareous nannofossil and one stable isotope studies on materials from Ocean Drilling Program (ODP) Legs 183 (Site 1135), 206 (Site 1256), and 207 (Site 1259) that target two important paleoceanographic events: 1) the middle/late Miocene carbonate crash, and 2) the Paleocene/Eocene Thermal Maximum (PETM). Site 1256 nannofossil biostratigraphy in Chapter 1 refined the author's shore-based shipboard Quaternary-middle-Miocene nannofossil biostratigraphy... Show moreThis dissertation is a collection of five calcareous nannofossil and one stable isotope studies on materials from Ocean Drilling Program (ODP) Legs 183 (Site 1135), 206 (Site 1256), and 207 (Site 1259) that target two important paleoceanographic events: 1) the middle/late Miocene carbonate crash, and 2) the Paleocene/Eocene Thermal Maximum (PETM). Site 1256 nannofossil biostratigraphy in Chapter 1 refined the author's shore-based shipboard Quaternary-middle-Miocene nannofossil biostratigraphy with 16 zones/combined zones recognized based on 28 nannofossil datums. This chapter provides a chronologic framework for the age calibration of the first occurrence (7.18 Ma) and last occurrence (6.32 Ma) of Reticulofenestra rotaria, calculation of linear sedimentation rates, age determination of basalt basement (~14.5 Ma), and the recognition of the "carbonate crash" paleoceanographic event at the middle/late Miocene boundary. Reworked nannofossils and lithologic changes also allow a reading of a three-episode redepositional history (4.7, 8.3, and 10.7 Ma, respectively) in the eastern Pacific. The detailed examination of the Site 1256 material also yielded well-preserved Discoaster stellulus, for which only the distal view had been depicted in the original description. In Chapter 2, a redescription and re-illustration of both sides of this asterolith is provided. This should prevent misidentification of specimens in proximal view, thereby raising its potential application for middle-late Miocene biostratigraphy. Based on the above age model, in Chapter 3 stable oxygen and carbon isotopes were used for the first time to explore the late/middle Miocene "carbonate crash". This carbonate transition is a widespread (eastern and central equatorial Pacific, Indian, South Atlantic, and the Caribbean), sharp decrease in carbonate mass-accumulation rates, which has previously been considered only a dissolution event. The positive correlation (R2 = 0.75) between d13C and CaCO3 mass accumulation rates during 5-14 Ma at ODP Site 1256 clearly demonstrates that carbonate accumulation is mainly biologically controlled. The coincidence of the carbonate crash with negative excursions in d13C and d18O values suggests a causative mechanism related to surface-water productivity, as a result of surface-water warming and reduced upwelling. Based on these observations, one could speculate that the major middle/late Miocene sea-level drop may have caused the complete closure of the Indonesian Seaway, resulting in a piling-up of surface warm water in the west Pacific. The eastward spread of this nutrient-poor water then would have warmed sea-surface temperatures and reduced upwelling in the central and eastern Pacific, thereby creating a prolonged "El Nino" scenario and reducing biological productivity of phytoplankton. The reduction in carbonate supply to the deep waters consequently caused a rapid shoaling of the carbonate compensation depth, thereby triggering the carbonate crash. The PETM was a catastrophic, rapid greenhouse-forced global warming event ~55 m.y. ago that triggered an abrupt turnover in ocean chemistry and circulation as well as biota. Chapter 4 represents a quantitative study of the response of nannoplankton to the PETM at Demerara Rise, equatorial Atlantic (Site 1259). Toweius, Fasciculithus, and Chiasmolithus sharply decrease at the onset of the PETM, whereas Chiasmolithus, Markalius cf. M. apertus, and Neochiasmolithus thrive immediately after the event, which also signals the successive first appearances of Discoaster araneus, Rhomboaster, and Tribrachiatus. Two main environmental factors were extracted by correspondence analysis of relative abundance data. The time series of the two factors shows that during the PETM, 1) environmental stress (most likely from changes in seawater pH) increased and may well have also induced the evolution of ephemeral nannofossil "excursion taxa"; and 2) surface-water productivity increased at this site presumably due to higher runoff from continental areas. The local phytoplankton opportunist, Markalius cf. M. apertus, is described as a new species in Chapter 5, which will be published under the name Coccolithus bownii. Results presented in Chapter 6 from Site 1135 on the Kerguelen Plateau, Southern Ocean suggest that nannoplankton responded differently to the PETM at southern high latitudes. The onset of the carbon isotope excursion occurs within an 18-cm interval (instead of 1-2 cm as observed in most deep-sea sections) before the peak is reached, displaying a linear mixing curve. This indicates that the release of light carbon was a gradual, single injection, instead of multiple pulses as suggested in previous work, and that this sequence is highly expanded as a result of high sedimentation rates at this relatively shallow oceanic site. This is evidenced by the high numbers of dissolution-susceptible holococcoliths (Zygrhablithus bijugatus) preserved throughout the sequence. Although r- and K-selected specialists exponentially increase in abundance at the onset, Chiasmolithus abruptly drops but then rapidly recovers, whereas Discoaster and Fasciculithus show opposite trends, indicating that in high latitudes, surface-water oligotrophy prevailed at the carbon isotope excursion (CIE) onset but mesotrophic conditions dominated the CIE recovery. These observations confirm previous results from ODP Site 690 on Maud Rise. The intensive dissolution of susceptible holococcoliths and the poor preservation of the assemblages are believed to have been caused by the effects of corrosion caused by the methane release. The different responses of nannoplankton to the PETM and the contrasts evident in previous work from the open ocean vs the continental margins further demonstrate that the response to the PETM can be influenced by local differences in geologic setting and oceanographic conditions. Show less

Date Issued

2007

Identifier

FSU_migr_etd-3512

Format

Thesis

Title

Are Subterranean Estuaries a Source of Chromophoric Dissolved Organic Matter (CDOM) to the Coastal Ocean?: A Case Study in the Northern Gulf of Mexico.

Submarine groundwater discharge (SGD) is a major pathway for nutrient transport in coastal marine systems. There are indications that SGD may also release large amounts of dissolved organic matter (DOM) to the coastal ocean and thus impact coastal ecosystem functioning. DOM is usually quantified as dissolved organic carbon (DOC), which requires discrete sampling. Therefore, detailed time series on tidally-driven SGD cannot easily be obtained for DOC. The chromophoric component of DOM (CDOM)... Show moreSubmarine groundwater discharge (SGD) is a major pathway for nutrient transport in coastal marine systems. There are indications that SGD may also release large amounts of dissolved organic matter (DOM) to the coastal ocean and thus impact coastal ecosystem functioning. DOM is usually quantified as dissolved organic carbon (DOC), which requires discrete sampling. Therefore, detailed time series on tidally-driven SGD cannot easily be obtained for DOC. The chromophoric component of DOM (CDOM) can be monitored via specific fluorescence in high temporal resolution and in situ. Here we hypothesize that SGD is a significant source of CDOM to the coastal ocean, impacting optical properties and biogeochemical cycles of coastal waters. In this context we also evaluated the possibility of using CDOM as a proxy for DOC in a subterranean estuary. To test our hypothesis, a case study was performed in a shallow bay in the Northern Gulf of Mexico. CDOM was continuously monitored in situ for approximately three weeks in a groundwater well on a beach and 300 m offshore in the adjacent bay. The radon isotope 222Rn was also continuously measured as a conservative tracer for submarine groundwater in the bay. Discrete samples for DOC analysis and associated variables were collected to cover one tidal cycle (15 hours). In a simple SGD model, CDOM concentrations in the bay were predicted by multiplying 222Rn concentrations in the bay (as a measure for SGD) with CDOM concentrations in the well (as the groundwater endmember). This was done for each hour during the entire sampling period. If a lag-time of one hour between groundwater and bay was considered, the predicted CDOM significantly correlated (p<0.01) with the measured CDOM in the bay. Independent statistical tests, including chlorophyll a, salinity and water level data, confirm this finding and demonstrate that CDOM in the bay is mainly driven by freshwater SGD. More detailed analysis of the time series data show that short-term time series of 24 hours or less can lead to erroneous results in estimating SGD. CDOM and DOC significantly correlated for the groundwater endmember, and CDOM could thus be transformed into DOC concentrations. It was estimated that at least 0.6 Mega-mole DOC are delivered to the entire Gulf Coast of Florida in a day via SGD which is similar in order of magnitude as riverine fluxes. Show less

Paleoceanographic proxy data indicate that the Agulhas leakage into the South Atlantic was dramatically reduced during glacial times. In our former papers, we suggested that this was due to a northward shift of the zero wind stress curl that, in turn, forced the retroflection to occur farther north, where the slant of the coastline relative to the north is steep. In the present paper, we propose that strong westerlies (0.4 Pa, implying a wind speed of ~ 12 m s-1 at zero degrees centigrade),... Show morePaleoceanographic proxy data indicate that the Agulhas leakage into the South Atlantic was dramatically reduced during glacial times. In our former papers, we suggested that this was due to a northward shift of the zero wind stress curl that, in turn, forced the retroflection to occur farther north, where the slant of the coastline relative to the north is steep. In the present paper, we propose that strong westerlies (0.4 Pa, implying a wind speed of ~ 12 m s-1 at zero degrees centigrade), which were supposedly common during glaciations, can also arrest the leakage. This arrest occurred because the wind stress opposed the momentum flux associated with the retroflection; such an arrest did not require the retroflection to shift in latitude. We use a simple, nonlinear, "reduced gravity" model to show analytically and numerically that, under the above conditions, the eastward wind stress compensates for the zonal westward flow-force associated with the retroflection, thus avoiding the development and shedding of rings. For a nearly zonal wall, westerly winds, and small upper layer thickness along the wall, the arresting wind stress is found, theoretically, to be, τx~0.042α3/2ρf[(2fQ)3/g']1/4 where α is twice the retroflection eddy vorticity, ρ the water density, and Q the Agulhas Current volume flux; the remaining notation is conventional. Show less

Lightning data provide a valuable tool for examining interactions between multi-scale weather phenomena. Weather events are determined by complex atmospheric interactions at various spatial and temporal scales. Long-term climatologies facilitate discussion of average meteorological conditions and can help isolate the relative influence of multi-scale systems (e.g., synoptic scale, mesoscale, etc.) on local weather patterns. Lightning datasets allow the development of large-scale, long-term... Show moreLightning data provide a valuable tool for examining interactions between multi-scale weather phenomena. Weather events are determined by complex atmospheric interactions at various spatial and temporal scales. Long-term climatologies facilitate discussion of average meteorological conditions and can help isolate the relative influence of multi-scale systems (e.g., synoptic scale, mesoscale, etc.) on local weather patterns. Lightning datasets allow the development of large-scale, long-term climatologies. These lightning climatologies then are compared with additional atmospheric observations (e.g., numerical models and radar) to examine the regional, seasonal, and storm-scale variability of thunderstorm characteristics. The National Lightning Detection Network (NLDN) underwent a major upgrade during 2002–2003 that increased its sensitivity and improved its performance. Therefore, this study applies the same methodology to pre- and post-upgrade NLDN datasets to allow direct quantitative comparisons between them and thereby examine the influence of the recent upgrade on regional distributions of cloud-to-ground (CG) lightning characteristics. Although seasonal variability must be understood to better define apparent relationships between storm properties and lightning production, seasonal differences are best described on the regional scale. Therefore, this study also examines Florida's seasonal, regional, and storm-scale CG variability during 2004–09. Since lightning data are recorded instantaneously and typically reported every minute, they also provide valuable information on storm-scale development and evolution. Automated procedures are developed to create grids of lightning and radar parameters, cluster individual storm features, and data mine the lightning and radar attributes of many individual storms. These procedures facilitate detailed analysis of relationships between lightning and radar-derived parameters in many individual storms in the Mid-Atlantic Region during 2007–09. A major goal of this research is to combine information about the near-storm environment, radar-defined storm structure, and both intra-cloud (IC) and CG lightning characteristics to better quantify relationships between storm structure, lightning production, and storm severity. Show less

The hyper-spectral Cross-track Infrared Sounder (CrIS) on board Suomi National Polar-orbiting Partnership (NPP) supports a continuing advance in numerical weather prediction (NWP) for improved short- to medium-range weather forecast skills. The assimilation of CrIS brightness temperature observations in NWP modeling systems requires the data biases be properly estimated and removed from data. Both the solar radiation reflected by sea surface into the satellite viewing direction and the solar... Show moreThe hyper-spectral Cross-track Infrared Sounder (CrIS) on board Suomi National Polar-orbiting Partnership (NPP) supports a continuing advance in numerical weather prediction (NWP) for improved short- to medium-range weather forecast skills. The assimilation of CrIS brightness temperature observations in NWP modeling systems requires the data biases be properly estimated and removed from data. Both the solar radiation reflected by sea surface into the satellite viewing direction and the solar pumping that deviates the stratosphere from the local thermal equilibrium (LTE) introduce the significant biases in CrIS infrared shortwave observations. In this study, the effects of sun glint and nonlocal thermal equilibrium (NLTE) on CrIS data biases are assessed quantitatively. It is found that the newly-developed sun glint and NLTE models can dramatically reduce the CrIS data biases at infrared shortwave band during daytime. However, the biases still remain relatively large for CrIS infrared shortwave stratospheric channels after the NLTE correction. A further study confirms that the bias residuals after the NLTE correction mainly come from the input temperature profiles to the Radiative Transfer Model (RTM) not the RTM itself. It is found that the temperature profiles from the National Center for Environmental Prediction (NCEP) Global Forecast System (GFS), which serve as input to the Community Radiative Transfer Model (CRTM), have large cold biases in the upper stratosphere, leading to the large bias remnants of stratospheric channels. Compared with the temperature profiles from ERA Interim reanalysis, the cold biases of GFS temperature profiles increase with altitude and reach about 10 K near 1 hPa. Show less

A two-phase study of the potential impact of Geosynchronous Imaging Fourier Transfer Spectrometer (GIFTS) radiance data to the prediction of strong convective events was developed. In the first phase of the project, a statistical analysis of six runs of the Fifth Generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5), version 3, was performed. These runs incorporate different size domains, numbers of vertical levels, numbers of nesting domains,... Show moreA two-phase study of the potential impact of Geosynchronous Imaging Fourier Transfer Spectrometer (GIFTS) radiance data to the prediction of strong convective events was developed. In the first phase of the project, a statistical analysis of six runs of the Fifth Generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5), version 3, was performed. These runs incorporate different size domains, numbers of vertical levels, numbers of nesting domains, and physical schemes. Using high-resolution National Center for Environmental Prediction (NCEP) Stage IV precipitation estimates, mesonet data, and radar reflectivity, it was determined that of all runs, one was chosen as being most appropriate for simulating GIFTS radiance. This run incorporates the simple ice microphysical scheme, the Grell cumulus scheme, the Blackadar planetary boundary layer scheme, and a simple atmospheric radiation scheme. Furthermore, this run was nested, with the mother domain (12-km resolution) of size 163 x 127 x 54 and the nested domain (4-km resolution) of size 103 x 127 x 54. In the second phase of the project, two sensitivity studies were carried out. In the first sensitivity study, the sensitivity of simulated GIFTS radiance to temperature and water vapor were examined. The 14 most sensitive channels within the GIFTS spectral range, out of 3,073, were chosen for further analysis. Through an analysis of an MM5 grid point that had relatively minimal cloud cover, it was determined that the most sensitive atmospheric layers at eight channels are in the lower troposphere (temperature) and lower to mid-troposphere (water vapor). At the other six, the most sensitive region is in the mid- to upper troposphere. The layers of maximum sensitivity are consistent with peaks of the weighting functions of these channels. The second sensitivity study examined the sensitivity of convective precipitation forecasts to the initial conditions of temperature and water vapor. The purpose of this study was to "bridge" the results of the first sensitivity study to the MM5 quantitative precipitation forecast (QPF) results. It was found that the most sensitive region is over the Central Plains of the United States and that the convective QPF is most sensitive to both water vapor content and temperature in the low-levels of the troposphere. Furthermore, temperature is deemed more sensitive to convective QPFs than water vapor. The results from these sensitivity tests, when linked together, demonstrate that GIFTS radiance at the eight wavenumbers most sensitive in the lower troposphere may be more effective to improve QPF than higher wavenumber radiance and that temperature in the Central Plains is the key meteorological variable to which the convective QPF is most sensitive. In a future four-dimensional variational data assimilation (4D-Var) study, simulated and real atmospheric observations from various sources will be assimilated into the MM5, with the GIFTS model representing the observation operator. Through this current study, a better sense of the utility of data from GIFTS to the forecasting of convective precipitation is ascertained, which would help streamline the 4D-Var study. Show less

Groundwater-surface water interactions in lakes have been gaining attention in recent years as scientists have recognized the potential significance that groundwater has as a source of nutrients and contaminants to aquatic ecosystems. Such interactions need to be understood in order for us to protect important ecosystems and quantify nutrient loading into lakes. This project set out to test the idea that good estimates could be made of groundwater inputs into Florida lakes using a simple... Show moreGroundwater-surface water interactions in lakes have been gaining attention in recent years as scientists have recognized the potential significance that groundwater has as a source of nutrients and contaminants to aquatic ecosystems. Such interactions need to be understood in order for us to protect important ecosystems and quantify nutrient loading into lakes. This project set out to test the idea that good estimates could be made of groundwater inputs into Florida lakes using a simple geochemical tracer technique. We hypothesize that a relatively small number of measurements would be sufficient to provide a reasonably good (a factor of 2) estimate of groundwater discharge. Naturally occurring 222Rn makes an ideal tracer because it exists in enriched concentrations in groundwater relative to surface water. We used Lake Barco, a small seepage lake in the Katherine Ordway Preserve, for a detailed pilot study in order to test this hypothesis. The preserve is located about 34 km east of Gainesville, Florida and makes an excellent research site because it is maintained in a pristine state as it is closed off to public access. Two intensive samplings were completed, one in the "dry" season (March 2002) and one in the "wet" season (August 2003). In addition, periodic sampling trips were made to the lake every few weeks to evaluate the spatial and temporal patterns of radon distribution. A 222Rn mass balance was constructed for the lake to evaluate radon fluxes. Once the 222Rn fluxes were determined, groundwater inputs were estimated by dividing these fluxes by the concentration of radon in the water seeping into the lake. The radon concentration is estimated by sediment equilibration experiments using grab samples of sediment and radon activity measurements from monitor wells. We also constructed a traditional hydrologic water budget for Lake Barco. All hydrological variables were either measured or estimated and substituted into a water balance equation, which was then solved for the net groundwater flow term. These estimates were then compared to those from the 222Rn model. Our 222Rn measurements show little discernible spatial variation of radon inventories in the lake on any given day of sampling. Inventories measured at five different stations during the two different intensive sampling trips were all within ±13% of the mean value for each sampling. This amount of variation is considered insignificant, as the estimated analytical variation for the radon measurements is ±10%. We also found that we can estimate the lake inventory at any one station by collecting triplicate samples approximately one meter over the bottom at a single central sampling station. However, our results did display significant temporal variability, responding to rainfall trends that can influence the recharge rates. So, in a lake the size of Lake Barco (12 ha), reasonable groundwater discharge estimates at any given time can be made by triplicate analysis of radon in near-bottom waters and collection and processing of a few sediment samples. The estimations of groundwater discharge to the lake over the period of our study were, on average, 13,000 m3/month and 18,000 m3/month for the radon model and hydrologic budget, respectively. The water balance based estimate might be somewhat low due to differences in hydrogeologic movement under such dry conditions or the large error associated with budget estimations. Considering the large uncertainties in estimating groundwater flow via a hydrologic budget, agreement within a factor of two is considered satisfactory. Show less

Radiance data obtained from NASA's Advanced Infrared Sounder (AIRS) is used in an attempt to improve the mesoscale prediction of temperature and moisture using one- and four-dimensional variational data assimilation (1D/4D-Var). The joint National Center for Atmospheric Research and Pennsylvania State University fifth-generation mesoscale model (MM5) along with the Stand-alone AIRS Radiative Transfer Algorithm (SARTA) is selected for this project. This work aims to utilize AIRS "clear-channel... Show moreRadiance data obtained from NASA's Advanced Infrared Sounder (AIRS) is used in an attempt to improve the mesoscale prediction of temperature and moisture using one- and four-dimensional variational data assimilation (1D/4D-Var). The joint National Center for Atmospheric Research and Pennsylvania State University fifth-generation mesoscale model (MM5) along with the Stand-alone AIRS Radiative Transfer Algorithm (SARTA) is selected for this project. This work aims to utilize AIRS "clear-channel" radiances to enhance the first-guess analysis regarding the temperature and moisture content as a precursor to improving short-term precipitation forecasts. The adjoint operator for SARTA has been derived and linked to the MM5 adjoint modeling system; a "clear-channel" identification scheme, which is compatible with SARTA, has been developed and verified; and a set of one-dimensional variational data assimilation (1D-Var) experiments have been done in order to determine the impact of AIRS channels on the vertical profiles of temperature and moisture. Lastly, a preliminary 4D-Var experiment is carried out to determine the impact of a limited number of clear-channel AIRS radiances on the prediction of temperature and moisture. An adjoint-sensitivity based forecast verification technique is used to compare the 4D-Var forecast results to a control forecast. Show less

Unlike conventional and satellite observations, the Global Positioning System (GPS) radio occultation (RO) techniques provide all-weather, high-vertical-resolution observations that require no calibration. In this dissertation, the assimilation of GPS RO data is studied using the National Centers for Environmental prediction (NCEP) three dimensional variational analysis system. Three GPS data assimilation choices are considered and compared. A set of GPS bending angle assimilation (BA)... Show moreUnlike conventional and satellite observations, the Global Positioning System (GPS) radio occultation (RO) techniques provide all-weather, high-vertical-resolution observations that require no calibration. In this dissertation, the assimilation of GPS RO data is studied using the National Centers for Environmental prediction (NCEP) three dimensional variational analysis system. Three GPS data assimilation choices are considered and compared. A set of GPS bending angle assimilation (BA) experiments is first carried out and sensitivity of BA results to the observational weighting, the quality of the background fields, the variation of the gravity, and the vertical resolution of the GPS data are investigated. The GPS local refractivity assimilation (REF) is then conducted and compared with BA. Although REF is computationally cheaper than BA, the bias and root mean square errors of the background fields are more significantly reduced by BA than REF. Differences between GPS refractivity and bending angle assimilations are larger in thick-layered cloud systems (e.g., convective clouds in the mid-latitudes and cumulus clouds in the tropics) than in thin clouds and clear sky, which are found to be associated with the strength of horizontal gradient of the atmospheric refractivity. Aiming at achieving both accuracy and computational efficiency, a new observation operator that simulates the GPS excess phase delay is proposed and tested for GPS RO data assimilation. Using the excess phase delay, the along-track refractivity and refractivity gradient information can be included while the computational cost is kept low. Numerical results from the forward simulation and data assimilation using the excess phase delay (PHA) are compared with those of REF. PHA tends to produce a warmer and wetter model atmosphere, with finer structures and larger radii of influence than REF. Compared to GPS observations, simulations and analyses produced by PHA are more accurate than those of REF. It is also pointed out that under the assumption of the spherical symmetry of the local refractivity, the observation operator for the excess phase delay simplifies into a point scheme in which only a vertical profile of model refractivity is required. Show less

The availability of high resolution temperature and water vapor data is critical for the study of mesoscale scale weather phenomena (e.g., convective initiations, and tropical cyclones). As hyperspectral infrared sounders, the Atmospheric Infrared Sounder (AIRS) and Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) could provide high resolution atmospheric profiles by measuring radiations in many thousands of different channels. This work focuses on the assessment of the potential... Show moreThe availability of high resolution temperature and water vapor data is critical for the study of mesoscale scale weather phenomena (e.g., convective initiations, and tropical cyclones). As hyperspectral infrared sounders, the Atmospheric Infrared Sounder (AIRS) and Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) could provide high resolution atmospheric profiles by measuring radiations in many thousands of different channels. This work focuses on the assessment of the potential values of satellite hyperspectral radiance data on the study of convective initiations (CI) and the assimilation of AIRS radiance observations within tropical storms. First, the potential capability of hyperspectral infrared measurements (GIFTS) to provide convective precipitation forecasts has been studied and assessed. Using both the observed and the model-predicted profiles as input to the GIFTS radiative transfer model (RTM), it is shown that the simulated GIFTS radiance could capture the high vertical and temporal variability of the real and modeled atmosphere prior to a convective initiation, as well as the differences between observations and model forecasts. This study suggests the potential for hyperspectral infrared radiance data to make an important contribution to the improvement of the forecast skill of convective precipitation. Second, as the first step toward applying AIRS data to tropical cyclone (TC) prediction, a set of dropsonde profiles during Hurricane Rita (2005) is used to simulate AIRS radiance data and to assess the ability of AIRS data in capturing the vertical variability within TCs through one-dimensional variational (1D-Var) twin experiments. The AIRS observation errors and background errors are first estimated. Five sets of 1D-Var twin experiments are then performed using different combinations of AIRS channels. Finally, results from these 1D-Var experiments are analyzed. Major findings are: (1) AIRS radiance data contain useful information about the vertical variability of the temperature and water vapor within hurricanes; (2) assimilation of AIRS radiances significantly reduced errors in background temperature in the lower troposphere and relative humidity in the upper troposphere; (3) the near-real time (NRT) channel set provided by NOAA/NESDIS seems sufficient for capturing the vertical variability of the atmosphere in the upper troposphere of TCs, but not in the lower troposphere; and (4) the channels with weighting functions peak within the layer between 500-700 hPa could provide useful information to the atmospheric state below 700 hPa. A channel selection method is proposed to capture most vertical variability of temperature and water vapor within TCs contained in AIRS data. Finally, AIRS radiance data within TCs have been assimilated in the 1D-Var experiments with comparisons of the retrieval temperature and water vapor profiles with co-located Global Positioning System (GPS) radio occultation (RO) soundings and dropsonde profiles. The comparisons of AIRS 1D-Var retrieval profiles with GPS RO sounding show that AIRS data can greatly improve the analysis of temperature and water vapor profiles within TCs. The comparisons of retrieval profiles with dropsonde data during Hurricane Rita, however, showed some discrepancies partly due to the difference of these two measurements and the uncertainties of the AIRS errors. Show less

Date Issued

2010

Identifier

FSU_migr_etd-1326

Format

Thesis

Title

Atlantic Reconnaissance Vortex Message Climatology and Composites and Their Use in Characterizing Eyewall Cycles.

There has been great energy focused on tropical cyclone intensity forecasting over the past thirty years. Toward the goal of providing more accurate intensity forecasts, the role of the environment of a tropical storm has been studied at great length over the past few years while the storm itself has not. There remains considerable work left toward understanding how the tropical cyclone structure itself can be used to aid intensity forecasting. One step toward this goal for the Atlantic is by... Show moreThere has been great energy focused on tropical cyclone intensity forecasting over the past thirty years. Toward the goal of providing more accurate intensity forecasts, the role of the environment of a tropical storm has been studied at great length over the past few years while the storm itself has not. There remains considerable work left toward understanding how the tropical cyclone structure itself can be used to aid intensity forecasting. One step toward this goal for the Atlantic is by dissecting a climatology of reconnaissance vortex message reports from the Atlantic basin between 1989 and 2005. Such an analysis will permit the comparison of tropical cyclone core structure measurements to know future intensity change. This vortex message data, which is collected from dropsondes and radar during flights into tropical disturbances, includes eye size, pressure, eye temperature, eye dewpoint, maximum flight level winds and other pertinent information. The number of occurrences for each vortex message characteristic as well as frequency plots of eye type, Julian day, latitude, longitude, temperature, dewpoint, and intensity change as a function of mean sea level pressure (MSLP) and eye size were created. The composite mean eyewall cycle was analyzed, along with the cycles of concentric eyewalls and elliptical eyewalls. Based on this vortex message climatology and analysis, an eyewall phase diagram was developed that graphically shows the evolution of a storm. These eyewall phase diagrams show how eyewall cycles evolve in time using mean MSLP, mean eye size, concentric eyewall frequency, and elliptical eyewall frequency data. Case studies include analysis of a storm undergoing an eyewall replacement cycle (Rita 2005), a rapidly weakening storm (Charley 2004), and a rapidly intensifying storm (Wilma 2005). It was discovered in this study that core storm data collected from vortex data messages could be used to confirm theories on tropical cyclone intensity. Preliminary attempts at simple forecasts comparing eye characteristics and future intensity change were done. Indeed, short-term forecasts of intensity change should utilize storm-specific structure, beginning with an analysis of that structure in intensification versus weakening events. Further work involving pattern matching trajectories and trajectory segments to forecast future storm trajectory in the eyewall phase diagram may lead to helpful analog tropical cyclone intensity forecast guidance. Show less

By sampling individual rain events over a 1-year period at three sites situated around a known point source of atmospheric mercury, we have attempted to quantify its influence on local mercury deposition. A suite of trace elements was also analyzed on these rain event samples. A multi-element analytical program was set up using a Thermo-Finnigan "Element" ICP-MS. We identified 46 elements that are significantly enriched in rain samples relative to the method blank, including the alkali metals... Show moreBy sampling individual rain events over a 1-year period at three sites situated around a known point source of atmospheric mercury, we have attempted to quantify its influence on local mercury deposition. A suite of trace elements was also analyzed on these rain event samples. A multi-element analytical program was set up using a Thermo-Finnigan "Element" ICP-MS. We identified 46 elements that are significantly enriched in rain samples relative to the method blank, including the alkali metals and alkaline earth elements, all three rows of the transition metals, and the rare earth elements. The total mercury concentrations in the rainwater samples ranged from 2-40 ng/L. The volume weighted mean rainfall mercury concentrations ranged from 9.2-9.8 ng/L, and there were no significant differences in the rainfall Hg deposition between the three sites. Principal component factor analysis (PCFA) was used to evaluate co-variance between mercury and trace element deposition. PCFA showed a strong crustal factor, a strong sea-salt factor, a mysterious "P" factor and a strong mercury factor. The mercury factor linked mercury with Bi, Ga, Pb, Sb and V. Plume dispersion modeling and air-mass back trajectory analysis have been conducted for each rain event. The goal of this research was to use mercury and trace element relationships in an effort to identify, and quantify, the impacts from various emission sources in the region on rainfall chemistry. We calculated the annual integrated percent of mercury associated with coal burning ranging between 15-47%. Using models to estimate the impact of local deposition we found that less than 1% of the mercury we measured is from the known point source. Show less

A simple one-dimensional seasonal atmosphere-ocean energy balance model is used to study the seasonal and latitudinal response of the model climate to a doubling of the CO2 concentration. A new climate feedback analysis method, formulated in Lu and Cai (2009a), is used to isolate contributions (partial temperature changes) of the external forcing alone and subsequent feedbacks to the total temperature change experienced by the model climate. In this study, the relative importance of the... Show moreA simple one-dimensional seasonal atmosphere-ocean energy balance model is used to study the seasonal and latitudinal response of the model climate to a doubling of the CO2 concentration. A new climate feedback analysis method, formulated in Lu and Cai (2009a), is used to isolate contributions (partial temperature changes) of the external forcing alone and subsequent feedbacks to the total temperature change experienced by the model climate. In this study, the relative importance of the external forcing alone (the CO2 doubling), surface ice-albedo feedback, water vapor feedback, changes in poleward heat transport, changes in vertical sensible heat flux, and changes in heat storage are analyzed. The partial temperature change due to the water vapor feedback is substantially the largest contributor to the globally averaged surface warming. The ice-albedo feedback plays a smaller role, but also significantly contributes to the overall warming of the surface. The most important negative feedback, counteracting the surface warming, is the change in the vertical sensible heat flux. However, though the water vapor feedback is most responsible for the overall surface warming, it is not the feedback most responsible for the seasonal and spatial pattern of the surface warming. The climate of this model indicates that there is a surface polar warming amplification, with a maximum occurring in late summer/early fall. The feedback most responsible for this polar warming amplification and seasonal pattern in this model is the surface ice-albedo feedback, which is largest at high latitudes in summer. Show less

Simulations of baroclinic wave life cycles are performed in order to illustrate the wave evolution of a cyclone and diagnose possible unbalanced flow associated with the destabilization of an upper-level jet. Development of the baroclinic wave is observed using the multilevel primitive equation Weather Research and Forecasting (WRF) model. A baroclinic system is produced with an initially balanced, zonal baroclinic jet on an f-plane, whereby the geometry of the dynamic tropopause is specified... Show moreSimulations of baroclinic wave life cycles are performed in order to illustrate the wave evolution of a cyclone and diagnose possible unbalanced flow associated with the destabilization of an upper-level jet. Development of the baroclinic wave is observed using the multilevel primitive equation Weather Research and Forecasting (WRF) model. A baroclinic system is produced with an initially balanced, zonal baroclinic jet on an f-plane, whereby the geometry of the dynamic tropopause is specified. The change in geometry will result in different initial jet profiles. For each jet profile two numerical simulations comprised of different diffusion parameters are integrated to show the effect that the diffusion has on the simulation. The first simulation consists of a combination of weak horizontal and strong vertical diffusion, while the second simulation includes only strong horizontal diffusion, and is considered to be more consistent with real atmosphere characteristics. For each simulation, the nonlinear stage of the life cycle resembles a cyclonic wave-breaking system. Simulations where the vertical diffusion is strong tend to produce events of secondary cyclogenesis, which are not observed in the case of strong horizontal diffusion. Therefore, these secondary events are in all probability results of numerical instabilities at the triple point of the baroclinic system. The simulations with strong horizontal diffusion produce a crisper version of the baroclinic wave evolution cycle with sharper temperature gradients and deeper surface lows than the strong vertical diffusion case. Diagnostic calculations of the horizontal divergence and the residual of the nonlinear balance equation are shown in order to identify areas of unbalanced flow and subsequent inertia-gravity waves. Banded structures in the horizontal divergence field at the level of maximum wind speed suggest that the unbalanced flow is closely related to the upper level jet streak and possibly generated through geostrophic adjustment processes. The simulations with strong vertical diffusion contain less numerical noise and provide a clearer insight into the possible existence of inertia-gravity waves. A breakdown into the three main components of the residual of the nonlinear balance equation is shown in order to asses the contribution of each term towards the production of unbalanced flow, and indicates that the Laplacian term was the dominant factor as it was an order of magnitude stronger than the Jacobian and vorticity terms. Show less

The objective of this study is to quantify barrier layer development due to tropical cyclone (TC) passage using Argo float observations of temperature and salinity. To accomplish this objective, a climatology of Argo float measurements is developed from 2001-2014 for the Atlantic, eastern Pacific, and central Pacific basins. Each Argo float sample consists of a pre-storm and post-storm temperature and salinity profile pair. In addition, a no-TC Argo pair dataset is derived for comparison to... Show moreThe objective of this study is to quantify barrier layer development due to tropical cyclone (TC) passage using Argo float observations of temperature and salinity. To accomplish this objective, a climatology of Argo float measurements is developed from 2001-2014 for the Atlantic, eastern Pacific, and central Pacific basins. Each Argo float sample consists of a pre-storm and post-storm temperature and salinity profile pair. In addition, a no-TC Argo pair dataset is derived for comparison to account for natural ocean state variability and instrument sensitivity. The Atlantic basin shows a statistically significant increase in post-TC barrier layer thickness (BLT) and barrier layer potential energy (BLPE) that is largely attributable to an increase of 2.6 m in the post-TC isothermal layer depth (ITLD). The eastern Pacific basin shows no significant changes to any barrier layer characteristic, likely due to a shallow and highly stratified pycnocline. However, the near-surface layer freshens in the upper 30 m after TC passage, which increases static stability. Finally, the central Pacific has a statistically significant freshening in the upper 20-30 m that increases upper-ocean stratification by ~35%. The mechanisms responsible for increases in BLPE vary between the Atlantic and both Pacific basins; the Atlantic is sensitive to ITLD deepening, while the Pacific basins show near-surface freshening to be more important in barrier layer development. In addition, Argo data subsets are used to investigate the physical relationships between the barrier layer and TC intensity, TC translation speed, radial distance from TC center, and time after TC passage. ROMS model hindcasts of Hurricange Gonzalo (2014) characterize the upper-ocean response to TC precipitation forcing. Several different vertical mixing parameterizations are tested to determine their sensitivity to precipitation. For all mixing schemes, TC precipitation accounts for ocean surface freshening of about 0.3 PSU. The dominant terms in the near-surface salinity budget are the total advection and vertical diffusivity. The influence of precipitation-induced changes to the SST response is more complicated. In some areas, increased upper-ocean stratification mutes the SST cooling response. However, in other areas, cooling can be stronger when precipitation is prescribed. Dynamical changes in upper-ocean currents and the curl of the surface stress can induce a stronger cooling response in these regions. Show less

Date Issued

2018

Identifier

2019_Spring_Steffen_fsu_0071E_14955

Format

Thesis

Title

The Biochemical Composition of Naupii Derived from Stored Non-Diapause and Diapause Copepod Eggs and the Biology of Diapausing Eggs.

Mariculture of fish is needed to support our ever growing global population. Copepods are a natural and beneficial source of first feed for many marine fish species, but it can be difficult to hatch enough when the fish are ready to feed. Therefore, storage of copepod eggs for use at a later date increases the potential of nauplii to be used as a commercial food source. There are two types of eggs produced by copepods: diapause and non-diapause (or subitaneous). However, little is known about... Show moreMariculture of fish is needed to support our ever growing global population. Copepods are a natural and beneficial source of first feed for many marine fish species, but it can be difficult to hatch enough when the fish are ready to feed. Therefore, storage of copepod eggs for use at a later date increases the potential of nauplii to be used as a commercial food source. There are two types of eggs produced by copepods: diapause and non-diapause (or subitaneous). However, little is known about diapause or the effects and duration of storage, either under cold or warm temperature conditions, on the biochemical composition of nauplii. Little is also known about the development of embryos that enter diapause. Diapause requires a refractory period before development of the embryo continues. The refractory period can last for several months regardless of environmental conditions. I studied the effects of both cold storage and cold storage with the addition of antibiotics on non-diapause eggs of the copepod Acartia tonsa and duration of storage for diapause eggs produced by Centropages hamatus and compared those results to nauplii derived from non-diapause eggs. The organic components analyzed to determine if potential changes were occurring during storage were lipids, fatty acids, proteins, free amino acids, and carbohydrates as well as the percent hatch of the eggs and the dry weight of the resultant nauplii. To understand diapause, we utilized two stains, one to determine the number of nuclei present and another to determine intracellular pH of the diapausing eggs. Acartia tonsa eggs stored for up to15 days at 1°C did not indicate any change in the biochemical make-up of the resulting nauplii. The only change we observed was in the viability of the eggs, which decreased at a steady rate over time. The viability of the eggs quickly approached zero percent hatch beyond 15 days. The addition of the antibiotic oxytetracyclin at a 10% concentration did not change the naupliar biochemistry and did not increase viability over the storage time. Centropages hamatus eggs maintained a high level of viability over the course of 13 months of storage under anoxic conditions. The nauplii derived from the diapause eggs stored at 25°C had similar biochemical components regardless of the length of the storage period. My study indicates that storage of A. tonsa and C. hamatus may not affect the nutritional value of the nauplii for aquaculture purposes. We also determined that the embryos of C. hamatus stopped developing after ~7 cleavages. The diapausing embryos also maintained an intracellular pH similar to the surrounding water and acidified when beginning to develop. This is the first time the intracellular pH and only the third time the nuclei of a copepod diapausing egg has been determined. This information could allow future researchers to interrupt diapause and induce the eggs to hatch before the end of the refractory period. Show less

Carbon isotopes were used as tracers in the Florida Everglades to investigate the sources and sinks of dissolved organic carbon in natural and constructed wetlands and provide a way to monitor ecosystem restoration efforts. Stable carbon isotopes were used to determine the source of DOC and POC, and in a basic mass balance model to calculate turnover times of DOC in small constructed wetland cells. Radiocarbon was used to distinguish "old" DOC derived from historic peats from "new" DOC... Show moreCarbon isotopes were used as tracers in the Florida Everglades to investigate the sources and sinks of dissolved organic carbon in natural and constructed wetlands and provide a way to monitor ecosystem restoration efforts. Stable carbon isotopes were used to determine the source of DOC and POC, and in a basic mass balance model to calculate turnover times of DOC in small constructed wetland cells. Radiocarbon was used to distinguish "old" DOC derived from historic peats from "new" DOC derived from modern primary production. Our study suggests that Ä14C measurements can be a useful indicator of the progress of ecosystem restoration in the Everglades. The oxygen isotope of phosphate (P) can also serve as an isotopic tracer in wetlands. Initial method development to use the oxygen isotope of phosphate extracted from natural waters is presented here. Preliminary data indicates that microbial recycling is a major means by which P stays in the water column despite reducing anthropogenic contributions. Stable carbon isotopes were also used to quantify the percent of methane oxidized within Tallahassee landfill soils. Carbon isotope and oxidation data collected over almost 9 months of monitoring methane emissions from landfill surfaces with and without a "biocover" is examined. These measurements, combined with measurements of methane flux, can help monitor the efficiency of various treatments in reducing methane emissions to the atmosphere by enhancing oxidation of methane by methanogenic bacteria. The presence or absence of DOC in the water column can determine whether trace metals will be present as a nutrient or as a toxicant. A novel method coupling capillary electrophoresis with ICP-MS was used to separate metal species and calculate binding constants of rare earth elements and Th, Hf, and Zr with humic substances at a range of pH and ionic strength of 0.1. Equilibrium dialysis ligand exchange was performed to validate the CE-ICP-MS method. Conditional stability constants of tetravalent metal-HA complexes are several orders of magnitude higher than lanthanide-HA complexes. Because thorium is often used as a proxy for the tetravalent actinides, Th-HA binding constants are useful in the study of sequestration of actinides in nuclear repository settings. Show less

This study examines the changes in boundary layer of landfalling tropical cyclones. Several storms which made landfall near surface observation platforms capable of high resolution data storage were examined. These records were subjected to spectral methods to explore the characteristics of the changing boundary layer turbulence. These results were compared to recent observations of boundary layer roll features noted in some landfalling storms. Spectra were also used for determining... Show moreThis study examines the changes in boundary layer of landfalling tropical cyclones. Several storms which made landfall near surface observation platforms capable of high resolution data storage were examined. These records were subjected to spectral methods to explore the characteristics of the changing boundary layer turbulence. These results were compared to recent observations of boundary layer roll features noted in some landfalling storms. Spectra were also used for determining turbulence dissipation rates in the storms. It was determined that only the highest resolution datasets available with a sampling rate of 5 Hz were adequate to explore the small scale features of the flow and to accurately describe the turbulence dissipation rates. Show less

Date Issued

2004

Identifier

FSU_migr_etd-2653

Format

Thesis

Title

Broadband Solar Irradiances Measured on Fixed and Stabilized Platforms: Comparison of Observations and Their Uncertainties.

Over the past 40 years radiative transfer models have consistently under-predicted the amount of solar absorption by clouds. Estimates of the size of this discrepancy at the beginning of its discovery were ~10 W/m^2, but in 1995 jumped to 40-100 W/m^2, which ARESE I was formed to resolve. ARESE I being inconclusive, ARESE II was conducted and further studies brought the estimates back to ~10 W/m^2. Part of the problem lies with the difficulty of obtaining accurate measurements of the absorbed... Show moreOver the past 40 years radiative transfer models have consistently under-predicted the amount of solar absorption by clouds. Estimates of the size of this discrepancy at the beginning of its discovery were ~10 W/m^2, but in 1995 jumped to 40-100 W/m^2, which ARESE I was formed to resolve. ARESE I being inconclusive, ARESE II was conducted and further studies brought the estimates back to ~10 W/m^2. Part of the problem lies with the difficulty of obtaining accurate measurements of the absorbed solar insolation as well as constructing models that represent real atmospheric conditions. So after ARESE II was completed an experiment was performed to test the effectiveness of a new technique-the stabilized platform. A pyranomter mounted on a stabilized platform, which kept the instrument on board the Proteus aircraft in the earth's horizontal plane, was used to measure the solar flux. Another pyranomter, mounted on a standard fixed platform, was also aboard the Proteus. Since the observations of the fixed platform have to be corrected for the movements and deformation of the aircraft, there is an additional source of uncertainty. Thus the aim of this study was to determine the flux and absorption uncertainties observed from the fixed and stabilized platforms. The fixed platform flux uncertainties, at 4.4-14.8 W/m^2, were ~1.8 times those of the stabilized platform which were 3.8-8.2 W/m^2. However, the fixed flux uncertainties were not so great as to invalidate the pre-ARESE I and ARESE I studies Show less

A fully coupled regional downscaling system for both the Regional Spectral Model (RSM) for atmosphere and the Regional Ocean Modeling System (ROMS) for the ocean was developed for the purpose of downscaling observed analysis or global model outputs. The two models share the same grid and resolution with efficient parallelization through the use of dual message passing interfaces. Coupled downscaling was performed using historical Simple Ocean Data Assimilation (SODA) oceanic reanalysis and... Show moreA fully coupled regional downscaling system for both the Regional Spectral Model (RSM) for atmosphere and the Regional Ocean Modeling System (ROMS) for the ocean was developed for the purpose of downscaling observed analysis or global model outputs. The two models share the same grid and resolution with efficient parallelization through the use of dual message passing interfaces. Coupled downscaling was performed using historical Simple Ocean Data Assimilation (SODA) oceanic reanalysis and NCEP/DOE (R-2) atmospheric reanalysis in order to study the impact of coupling on the regional scale atmospheric analysis. The results were subsequently compared with the uncoupled downscaling forced by the prescribed observed sea surface temperature (SST). An evaluation of the SST and ocean current from the coupled experiment yielded realistic small-scale oceanic features that are nearly absent in the oceanic reanalysis. Upwelling over the California coast is well resolved and comparable to findings obtained from high-resolution observations. The coupling impact on the atmospheric circulation mainly modulates the near surface atmospheric variables when compared to the simulation conducted without coupling. The duration of the Catalina Eddy detected in the coupled experiment increased by about 6.5% when compared to that in the uncoupled experiment. The offshore land breeze is enhanced by about 10%, whereas the change in the onshore sea breeze is very small during the summer. Show less

With the aid of a 3-part modeling system forced by various satellite-remote sensed atmospheric inputs controlled by cloudiness, this study: (1) describes the space-time variations of surface net CO2 flux exchange over the large scale Amazon basin, (2) determines the key factors controlling these variations, and ultimately (3) determines the optimal spatial configuration of a network of tower observing posts, which if deployed, could capture in area-wide averages the main variant properties of... Show moreWith the aid of a 3-part modeling system forced by various satellite-remote sensed atmospheric inputs controlled by cloudiness, this study: (1) describes the space-time variations of surface net CO2 flux exchange over the large scale Amazon basin, (2) determines the key factors controlling these variations, and ultimately (3) determines the optimal spatial configuration of a network of tower observing posts, which if deployed, could capture in area-wide averages the main variant properties of the Amazon basin's surface net carbon flux on an absolute basis. The philosophy guiding this research is that whereas a sufficiently detailed model can do very well in capturing the space-time gradients of carbon flux exchange and thus the relative source-sink properties of the Amazonian landscape, current modeling knowledge does not allow an adequate model determination of absolute source-sink properties. Direct observations are needed to obtain meaningful absolute accuracies of the source-sink properties, properties that are highly sensitive to environmental and bio-physiological factors that effectively produce a heterogeneous fabric of source and sink magnitudes across the basin at any given instant of time. However, for the Amazon basin, and as a general rule of thumb in carbon budget monitoring over a large expanse, there seems to be never enough observation posts to eliminate the systematic bias problem -- nor are those that do exist sited according to a network strategy that optimizes their collective ability to eliminate such a bias problem. A hydrometeorological model coupled to a mixed layer (ML) model of the planetary boundary layer (PBL) then equipped with a set of three CO2 assimilation models, and finally forced by high resolution satellite-retrieved incoming surface radiation fluxes and rainfall, forms a detailed carbon flux exchange modeling system linked to satellite inputs, that achieves the desired research objectives. The forcing of the model by remotely sensed solar/infrared radiative flux and rainrate variables, which exert dominant influences on the surface carbon budget and whose variant properties are determined by the position and diurnal timing of cloudiness, is an essential element of the modeling system. This is because one of the greatest shortcomings in prognostic modeling is the ability to reproduce real clouds, particularly convective clouds, in the right place at the right time. In understanding how environmental and bio-physiological factors exert their respective controls on carbon flux exchange variability, the underlying variables are classified into four categories: (1) meteorological factors; (2) radiation factors; (3) water cycle factors; and (4) bio-physiological factors. The three different CO2 assimilation models are investigated to achieve optimal performance insofar as obtaining validated surface carbon, heat, and moisture fluxes in the framework of the Florida State University (FSU) hydrometeorological model -- developed over the last decade by E.A. Smith & H.J. Cooper. Of the three carbon models examined, the one selected for the final net CO2 flux calculations was developed by G. Bonan, beginning with his Ph.D. dissertation research and now included in a land surface model (LSM) facility at NCAR. This carbon scheme contains a respiration component consistent with its photosynthetic component and physically couples the CO2, sensible, and latent heat fluxes through stomatal resistance. Test calculations of net ecosystem productivity (NEP) show that it is essential to model canopy-boundary layer interactions in order to reproduce observed morning CO2 effluxes measured at various forest sites located within Brazil and operated as part of the Large Scale Biosphere-Atmosphere Research Programme for Amazônia (LBA) -- specifically the LBA tower sites at Manaus and Jaru. This is because under typical conditions of a stable nocturnal PBL, the forest canopy remains stagnant, allowing carbon concentrations to become elevated until after sunrise when PBL stability flips and CO2 is rapidly vented into the atmosphere. In the PBL model developed for the study, CO2 concentrations and the concomitant fluxes are determined for five layers in and above the forest canopy following the progression of the ML during the daytime and the nocturnal boundary layer at night, which are treated as separate components of the diurnal PBL. It is important to point out that canopy heat capacity must be accounted for in the hydrometeorological modeling (an oft-overlooked factor in LSM modeling), to prevent sensible heat fluxes from being systematically overestimated. Values of observed canopy heat storage (needed in the development of the heat capacity scheme) are found using observed differences between net incoming radiation and sensible-latent heat fluxes, or observed total residual energy. Calibration and validation of CO2, sensible, and latent fluxes at the three LBA tower sites are accomplished using modeled total residual energy at the forest sites and modified photosynthesis parameters at the pasture site. Application of the modeling system over the large-scale Amazon basin shows that while vegetation type is the most important factor controlling area-wide CO2 fluxes, incoming surface solar radiation and ambient temperature (both directly responsive to the cloud field) are the primary factors producing spatial and temporal variability of CO2 fluxes at a given location. Modeled CO2 fluxes show mean monthly uptake values in the range of 1-3 mmol m-2 s-1. Due to the superimposed annual and daily march of the solar elevation angle, diurnal progressions of large coherent expanses of CO2 efflux over forest areas, progressing from SE to NW in December and from NE to SW in June, are an essential variational mode in the surface carbon budget. Inspection of area-wide modeled fluxes near the tower sites reveals that the systematic use of ECMWF-analyzed winds and temperatures in forcing the modeling system creates instances of spurious nocturnal stability that produce larger morning efflux magnitudes than observations suggest. Finally, CO2 fluxes at some 20,000 forest grid points within the Amazônia region and for eight months of model output, are analyzed to determine the optimal sampling configuration vis-à-vis capturing in area-wide averages, the space-time variability of net CO2 flux. These results lead to the conclusion that flux observations from five strategically placed towers, measuring in conjunction with the existing three LBA towers at Manaus and Jaru, would be sufficient in baselining area-wide net CO2 fluxes needed for an understanding of carbon sequestration within the Amazon basin on an absolute scale. Show less

This research project seeks to evaluate the rainfall forecast accuracy of the GEFS (Global Ensemble Forecast System) following the 2010 model update, analyzing the Atlantic September 2010 Hurricane Karl as a case study. Archived forecasted accumulated precipitation amounts from the GEFS are compared with archived CMORPH (CPC Morphing Technique) precipitation estimates. A sequence of 15 six hour forecasts from 1200 UTC 14 September 2010 to 1200 UTC 18 September 2010 are graphically displayed... Show moreThis research project seeks to evaluate the rainfall forecast accuracy of the GEFS (Global Ensemble Forecast System) following the 2010 model update, analyzing the Atlantic September 2010 Hurricane Karl as a case study. Archived forecasted accumulated precipitation amounts from the GEFS are compared with archived CMORPH (CPC Morphing Technique) precipitation estimates. A sequence of 15 six hour forecasts from 1200 UTC 14 September 2010 to 1200 UTC 18 September 2010 are graphically displayed using GrADS (Grid Analysis and Display System). Four images were produced for each of the 15 six-hour time frames: A) CMORPH 6-hour accumulated precipitation, B) GEFS 6-hour accumulated precipitation, C) Difference in GEFS and CMORPH 6-hour accumulated precipitation (GEFS-CMORPH), and D) Overlay of outlined areas of medium (≥0.25 inches) and heavy (≥1.0 inches) precipitation for the GEFS and CMORPH. Several errors in the precipitation forecast of the GEFS model post-update were consistent with errors found in the GEFS model prior to its 2010 update from previous studies. For example, the GEFS forecasted the size of the hurricane to be too large for all evaluated times. Although the six hour GEFS track forecast was closely aligned with that of the verified track, major differences between the forecast and verification occurred as the storm approached its second landfall in Mexico. This study highlights that although the model may accurately depict the storm track, other model biases such as a lower resolution, difficulty depicting the atmosphere near land/sea boundaries and over complex terrain—may significantly impact the precipitation forecast. Show less

Date Issued

2011

Identifier

FSU_migr_uhm-0011

Format

Thesis

Title

A Case Study of a Hybrid Cyclone: 6-9 September 2009.

Creator

Sliwinski, Timothy, Earth, Ocean & Atmospheric Science

Abstract/Description

Hybrid cyclones, such as subtropical storms and warm seclusions, are generally defined by the fact that they contain characteristics of the main types of cyclones: tropical and extratropical. This case study examines whether a cyclone can be considered hybrid without experiencing a transition from either of these two main types. The case in question occurred between 6 and 9 September 2009 before becoming frontal. The cyclone formed independently of other cyclones and was shallow warm-core at... Show moreHybrid cyclones, such as subtropical storms and warm seclusions, are generally defined by the fact that they contain characteristics of the main types of cyclones: tropical and extratropical. This case study examines whether a cyclone can be considered hybrid without experiencing a transition from either of these two main types. The case in question occurred between 6 and 9 September 2009 before becoming frontal. The cyclone formed independently of other cyclones and was shallow warm-core at its start. It would go on to exhibit properties of tropical cyclones such as a stacked surface warm-core and even convection occurring at the center. It would also go on to exhibit properties of extratropical cyclones by strengthening whenever an upper-level shortwave came near, increasing baroclinicity. This study looks at the large-scale patterns of development and utilizes the diagnostic properties of the terms of the quasi-geostrophic omega equation to understand the forcings in the area of the cyclone as depicted in the North American Regional Reanalysis. In addition, cyclone phase diagrams were generated for other analyses to determine whether the characteristics depict hybrid, extratropical, tropical, or subtropical development based on the parameters of thermal wind and thermal symmetry. It was found that the system was a hybrid system in that a warm-core surface cyclone did exist from the surface to 500 hPa; however upper-level short waves about an upper-level trough were responsible for providing forcing for the genesis and strengthening of this storm. Show less

Date Issued

2011

Identifier

FSU_migr_uhm-0038

Format

Thesis

Title

Case-Base Devaluation of a Physical Initialization Technique for Assimilating Precipitation in NWP.

A novel method for assimilating precipitation observations into a numerical weather prediction model is presented and evaluated for a case study of a monsoon rainfall event over the Asian subcontinent. The method, known as physical initialization (Krishnamurti et al. 1991), involves the iterative adjustment of the vertical moisture profile towards a configuration that would permit simulated precipitation where there is observed precipitation. The physical initialization procedure was... Show moreA novel method for assimilating precipitation observations into a numerical weather prediction model is presented and evaluated for a case study of a monsoon rainfall event over the Asian subcontinent. The method, known as physical initialization (Krishnamurti et al. 1991), involves the iterative adjustment of the vertical moisture profile towards a configuration that would permit simulated precipitation where there is observed precipitation. The physical initialization procedure was incorporated into the Weather Research and Forecasting (WRF) model. Evaluation of the technique was accomplished through the comparison of two simulations: one with the physical initialization and one without. Both simulations were evaluated against TRMM rainfall. The impact of physical initialization was shown to be beneficial to the two-day typical Indian Summer Monsoon case study with respect to the rainfall forecast skill as well as the mesoscale circulation and vertical redistribution of moisture. Specifically, the correlation between simulated and observed 3-hour accumulated precipitation is higher throughout the two-day forecast period in the run with physical initialization. The probability distribution of rainfall amounts in the run with physical initialization was also more similar to the observations, whereas the control WRF run exhibited a large bias of widespread light to moderate rain. Additionally, the run with physical initialization improves the forecast location of mesoscale precipitation features and removes regions of spurious rain from the forecast. Simulations were conducted and evaluated for this case only. Show less

Improved knowledge of thunderstorm behavior near the end of its lifecycle is essential to improving the prediction of lightning cessation. This study documents the characteristics of decaying storms near the end of their lightning activity at Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS). Total lightning data were obtained by combining information from the Lightning Detection and Ranging (LDAR) network with the Cloud-to-Ground-Surveillance System (CGLSS) and the... Show moreImproved knowledge of thunderstorm behavior near the end of its lifecycle is essential to improving the prediction of lightning cessation. This study documents the characteristics of decaying storms near the end of their lightning activity at Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS). Total lightning data were obtained by combining information from the Lightning Detection and Ranging (LDAR) network with the Cloud-to-Ground-Surveillance System (CGLSS) and the National Lightning Detection Network (NLDN). The lightning data were used in conjunction with WSR-88D radar data and Rapid Update Cycle (RUC) model analyses. The study focuses on a dataset of 116 isolated unicellular and multicellular storms during the warm-seasons (May-September) of 2000-2005. Twenty of the 116 storms were tracked through lightning cessation using the K-Means storm clustering and tracking algorithm within the Warning Decision Support System – Integrated Information (WDSS-II). This tracking yielded time-series of radar-derived, RUC-derived, and lightning parameters. Flash characteristics of the 116 storms showed trends during storm growth and dissipation; however, none exhibited clear relationships with the final flash. Although most storms experienced gradually decaying flash rates until cessation, two other cessation behaviors also were observed, making flash activity an unreliable indicator of cessation. Trends in composite reflectivity, reflectivity at three temperatures crucial to storm electrification (i.e., 0°C, -10°C, -20°C), storm thickness of 30 dBZ above -10°C, and vertical gradients of reflectivity were analyzed for 20 storms during the 8 min period prior to cessation to determine if any indicated imminent cessation. Results showed substantial variability in the decaying storms. Although these parameters decreased in most storms during the 8 min period, some increased. Distributions of the parameters at the last flash also were considered, but no clearly preferred value was evident at the last flash. Neither the inversion of lightning initiation criteria (e.g., 40 dBZ at -10°C) nor the descent of 45 dBZ below -10°C were found to be a useful indicator of cessation. Previously-documented lightning "bubbles" of LDAR sources were observed and were consistent with pulses in the intensifying updrafts. The last lightning "bubble" signatures were found to precede lightning cessation by ~35 min. Show less

Five years of cloud-to-ground (CG) lightning data (2002 – 2006) from the National Lighting Detection Network (NLDN) are examined to describe the nature of CG lightning in Florida. Our focus is on positive CG lightning (+CG; i.e., that which lowers positive charge from cloud to ground). Flash densities are computed on a 2×2 km grid for +CG and total CG during the warm season (May – September), the cool (cold) season (remaining months), and the entire year. The maximum annual total CG flash... Show moreFive years of cloud-to-ground (CG) lightning data (2002 – 2006) from the National Lighting Detection Network (NLDN) are examined to describe the nature of CG lightning in Florida. Our focus is on positive CG lightning (+CG; i.e., that which lowers positive charge from cloud to ground). Flash densities are computed on a 2×2 km grid for +CG and total CG during the warm season (May – September), the cool (cold) season (remaining months), and the entire year. The maximum annual total CG flash density of 28.1 flashes km-2 yr-1 is located just north of Tampa. Relative minima of cool season CG flash density extend from Tallahassee northeastward and south of the Tampa – Cape Canaveral corridor. +CG flash density shows a tendency towards greater values in the northwestern portion of the domain during both seasons. Two relative maxima of +CG flash densities are located near the Apalachicola National Forest in the panhandle (0.5 – 1.05 positive flashes km-2 yr-1), and near Naples in Southwest Florida (0.35 – 0.5 positive flashes km-2 yr-1). The median peak current and number of return strokes (multiplicity) of +CG and –CG flashes are quite different during the cool season, but are more similar during the warm season. The greatest peak current (~ 30 kA) and smallest multiplicity (~ 1.4) of +CG flashes occur during the cool season. The warm season is characterized by the smaller peak current (~ 20 kA) and larger multiplicity (> 1.5) of +CG flashes. Since +CG lightning is generally thought to consist of a single return stroke, our warm season multiplicities of ~1.7 are unexpected. This value may represent cloud pulses that are misclassified by the NLDN as weak peak current +CG flashes, or may actually describe characteristics of the CG lightning. The threshold for classifying these weak positive events recently was increased from +10 kA to +15 kA. An important finding is that greater than 40 % of all positive events (> 10 kA) in Florida during June, July, August, and October ranged between 10 kA – 15 kA. The unusual warm season characteristics of +CG lightning suggest that numerous ambiguous events are retained in our dataset, even when using the new threshold of +15 kA. Daily CG lightning patterns in Jacksonville and Miami were analyzed during March and July 2003. On a given day, there is more +CG lightning during March than July in both Jacksonville and Miami. Also, when lightning does occur, the percentage of positive flashes generally is greater in Jacksonville than Miami. 1.5) of +CG flashes. Since +CG lightning is generally thought to consist of a single return stroke, our warm season multiplicities of ~1.7 are unexpected. This value may represent cloud pulses that are misclassified by the NLDN as weak peak current +CG flashes, or may actually describe characteristics of the CG lightning. The threshold for classifying these weak positive events recently was increased from +10 kA to +15 kA. An important finding is that greater than 40 % of all positive events (> 10 kA) in Florida during June, July, August, and October ranged between 10 kA – 15 kA. The unusual warm season characteristics of +CG lightning suggest that numerous ambiguous events are retained in our dataset, even when using the new threshold of +15 kA. Daily CG lightning patterns in Jacksonville and Miami were analyzed during March and July 2003. On a given day, there is more +CG lightning during March than July in both Jacksonville and Miami. Also, when lightning does occur, the percentage of positive flashes generally is greater in Jacksonville than Miami. 10 kA) in Florida during June, July, August, and October ranged between 10 kA – 15 kA. The unusual warm season characteristics of +CG lightning suggest that numerous ambiguous events are retained in our dataset, even when using the new threshold of +15 kA. Daily CG lightning patterns in Jacksonville and Miami were analyzed during March and July 2003. On a given day, there is more +CG lightning during March than July in both Jacksonville and Miami. Also, when lightning does occur, the percentage of positive flashes generally is greater in Jacksonville than Miami. Show less

Date Issued

2007

Identifier

FSU_migr_etd-1928

Format

Thesis

Title

Characteristics of WTLN-Derived Lightning.

Creator

Saunders, Matthew, Earth, Ocean & Atmospheric Science

Abstract/Description

Many studies have used cloud-to-ground (CG), intracloud (IC), and total (CG + IC) lightning to investigate relationships between lightning and severe weather. Although the National Lightning Detection Network (NLDN) is the most common system used to detect lightning, it is limited to reporting only CG lightning over the continental United States. The WeatherBug Total Lightning Network (WTLN) is a global data set recently established by Earth Networks, Inc. that reports both CG and IC... Show moreMany studies have used cloud-to-ground (CG), intracloud (IC), and total (CG + IC) lightning to investigate relationships between lightning and severe weather. Although the National Lightning Detection Network (NLDN) is the most common system used to detect lightning, it is limited to reporting only CG lightning over the continental United States. The WeatherBug Total Lightning Network (WTLN) is a global data set recently established by Earth Networks, Inc. that reports both CG and IC lightning. WTLN has the potential to offer superior lightning data, although little research has compared WTLN information to other data sets like the NLDN. Using WTLN and NLDN data, distributions of stroke counts by polarity and peak current were plotted during a16-month study period near Cape Canaveral, FL. The WTLN data set showed an over detection of weak peak current strokes and under detection of strong peak current strokes. The WTLN data also exhibited higher overall stroke counts compared to NLDN. A case study of the Tuscaloosa-Birmingham tornado showed an opposite relation between WTLN and NLDN stroke counts. Compared to NLDN, the WTLN continually undercounted strokes during the lifecycle of the storm. While the number of counts was dissimilar, the two data sets correlated strongly (0.79) during the storm period. When the lightning was divided by polarity, WTLN showed a much greater detection of positive CG lightning than NLDN. Show less

Date Issued

2012

Identifier

FSU_migr_uhm-0055

Format

Thesis

Title

Characterization of Errors in Various Moisture Roughness Length Parameterizations.

Often the parameterization of the moisture roughness length is not seen as being important, as long as the parameterization seems reasonable; that is, it is within the rather considerable bounds of error for the data sets used to determine the parameterization. However, the choice of parameterization does influence height adjustments of humidity and calculations of turbulent heat fluxes. This paper focuses on the calculation of the turbulent heat fluxes using different parameterizations of... Show moreOften the parameterization of the moisture roughness length is not seen as being important, as long as the parameterization seems reasonable; that is, it is within the rather considerable bounds of error for the data sets used to determine the parameterization. However, the choice of parameterization does influence height adjustments of humidity and calculations of turbulent heat fluxes. This paper focuses on the calculation of the turbulent heat fluxes using different parameterizations of roughness length. Five roughness length parameterizations are examined herein. These parameterizations include wall theory; the Clayson, Fairall, Curry parameterization; the Liu, Katsaros, Businger parameterization; Zilitinkevich et al. parameterization; and the COARE3.0 parameterization. Turbulent heat fluxes are calculated from each parameterization of the roughness length and are compared to observed turbulent heat flux values. The bulk latent heat flux estimates have a much better signal to noise ratio than the sensible heat fluxes, and are therefore the focus of the comparison to observations. This comparison indicates how to improve the proportionality in the above roughness length parameterizations, which are causing modeled turbulent heat flux magnitudes to be too large in four of the five parameterizations. The modeled turbulent heat fluxes are evaluated again after the modification of the parameterizations. Significant improvements in both the bias and the root mean square error (RMSE) are seen. Three parameterizations see roughly the same improvements of around 17Wm^-2 in the bias and roughly 10Wm^-2 in the RMSE. The largest improvements are in the Liu, Katsaros, Businger parameterization with bias improvements of over 45Wm^-2 and a RMSE reduction of nearly 32Wm^-2. Show less